U.S. patent application number 15/405974 was filed with the patent office on 2018-05-10 for system and method for multi-parameter spectroscopy.
The applicant listed for this patent is NXGEN PARTNERS IP, LLC. Invention is credited to SOLYMAN ASHRAFI.
Application Number | 20180128739 15/405974 |
Document ID | / |
Family ID | 58690998 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180128739 |
Kind Code |
A9 |
ASHRAFI; SOLYMAN |
May 10, 2018 |
SYSTEM AND METHOD FOR MULTI-PARAMETER SPECTROSCOPY
Abstract
An apparatus for detecting a material within a sample includes a
light emitting unit for directing at least one light beam through
the sample. A plurality of units receive the light beam that has
passed through the sample and performs a spectroscopic analysis of
the sample based on the received light beam. Each of the plurality
of units analyze a different parameter with respect to the sample a
provide a separate output signal with respect to the analysis. A
processor detects the material with respect each of the provided
separate output signals.
Inventors: |
ASHRAFI; SOLYMAN; (PLANO,
TX) |
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Applicant: |
Name |
City |
State |
Country |
Type |
NXGEN PARTNERS IP, LLC |
Dallas |
TX |
US |
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Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20170138851 A1 |
May 18, 2017 |
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Family ID: |
58690998 |
Appl. No.: |
15/405974 |
Filed: |
January 13, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14875507 |
Oct 5, 2015 |
9784724 |
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15405974 |
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15348608 |
Nov 10, 2016 |
9645083 |
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14875507 |
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15049594 |
Feb 22, 2016 |
9714902 |
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15348608 |
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62278186 |
Jan 13, 2016 |
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62322507 |
Apr 14, 2016 |
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62365486 |
Jul 22, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 33/483 20130101;
G01N 33/6896 20130101; A61B 5/0075 20130101; G01N 2800/2821
20130101; G01N 33/487 20130101; G01N 2333/4709 20130101; G01N
21/6486 20130101; G01N 21/59 20130101; G01N 21/3581 20130101; G01N
21/21 20130101; G01N 21/65 20130101 |
International
Class: |
G01N 21/59 20060101
G01N021/59; G01N 21/3581 20060101 G01N021/3581; G01N 21/65 20060101
G01N021/65; G01N 21/64 20060101 G01N021/64; G01N 21/21 20060101
G01N021/21; G01N 33/483 20060101 G01N033/483; A61B 5/00 20060101
A61B005/00 |
Claims
1. An apparatus for detecting a material within a sample,
comprising: a light emitting unit for directing at least one light
beam through the sample; a plurality of spectroscopic units for
receiving the light beam that has passed through the sample and
performing a spectroscopic analysis of the sample based on the
received light beam, each of the plurality of spectroscopic units
analyzing a different parameter with respect to the sample a
provide a separate output signal with respect to the analysis; and
a processor for detecting the material with respect each of the
provided separate output signals.
2. The apparatus of claim 1, wherein the plurality of spectroscopic
units further comprises: a first spectroscopic unit for receiving
the light beam that has passed through the sample and performing a
polarization wave analysis to generate a polarization parameter
output signal; a second spectroscopic unit for receiving the light
beam that has passed through the sample and performing a wavelength
analysis to generate a wavelength parameter output signal; and a
third spectroscopic unit for receiving the light beam that has
passed though the sample and performing an orbital angular momentum
(OAM) spectroscopic analysis to generate an OAM parameter output
signal.
3. The apparatus of claim 1, wherein the plurality of spectroscopic
units further comprises: a first spectroscopic unit for receiving
the light beam that has passed through the sample and performing
Raman spectroscopy analysis to generate a Raman parameter output
signal; a second spectroscopic unit for receiving the light beam
that has passed through the sample and performing infrared
spectroscopy analysis to generate a infrared parameter output
signal; a third spectroscopic unit for receiving the light beam
that has passed though the sample and performing an orbital angular
momentum (OAM) spectroscopic analysis to generate an OAM parameter
output signal; and a fourth spectroscopic unit for receiving the
light beam that has passed through the sample and performing a
polarization wave analysis to generate a polarization parameter
output signal.
4. The apparatus of claim 1, wherein at least one of the plurality
of spectroscopic units comprises a dual comb spectroscopy unit
using paired coherent frequency combs for receiving the light beam
from the sample and performing dual comb spectroscopic analysis to
generate an output signal.
5. The apparatus of claim 1, wherein the plurality of spectroscopic
units further comprise: a first spectroscopic unit for receiving
the light beam and performing Raman sideband spectroscopy analysis
to generate a first output signal; a second spectroscopic unit for
receiving the light beam and performing colloidal particles
manipulation using OAM tweezers; and wherein the light beam
comprises an OAM endowed light beam.
6. The apparatus of claim 1, wherein at least one of the plurality
of spectroscopic units comprises: a first spectroscopic unit for
receiving the light beam and performing OAM spectroscopic analysis
that detects delocalized OAM associated with an envelope
wavefunction in a Bloch framework; and a second spectroscopic unit
for receiving the light beam and performing OAM spectroscopic
analysis that detects local OAM associated with atoms within the
sample.
7. The apparatus of claim 1, wherein the plurality of spectroscopic
units comprises: a first spectroscopic unit for receiving the light
beam that has passed through the sample and performing a
polarization wave analysis to generate a polarization parameter
output signal; a second spectroscopic unit for receiving the light
beam that has passed though the sample and performing an orbital
angular momentum (OAM) spectroscopic analysis to generate an OAM
parameter output signal; further wherein the processor detects a
unique signature for the material within the sample indicated by
the polarization parameter output signal and the OAM parameter
output signal.
8. The apparatus of claim 1, wherein the plurality of spectroscopic
units comprises: a first spectroscopic unit for receiving the light
beam that has passed though the sample and performing an orbital
angular momentum (OAM) spectroscopic analysis to generate an OAM
parameter output signal; and a second spectroscopic unit for
receiving the light beam that has passed though the sample and
performing fluorescence spectroscopic analysis to detect emission
spectra and excitation spectra within the sample and generate a
fluorescence parameter output signal.
9. The apparatus of claim 8, wherein the fluorescence spectroscopic
analysis holds the exciting radiation at a fixed wavelength and
measures the emitted fluorescent intensity as a function of
emission wavelength.
10. The apparatus of claim 1, wherein the plurality of
spectroscopic units comprises: a first spectroscopic unit for
receiving the light beam that has passed though the sample and
performing an orbital angular momentum (OAM) spectroscopic analysis
to generate an OAM parameter output signal; and a second
spectroscopic unit for receiving the light beam that has passed
though the sample and performing terahertz (THz) spectroscopic
analysis to generate a fluorescence parameter output signal.
11. The apparatus of claim 10, wherein the THz spectroscopic
analysis provides selective detection of weak inter-molecular and
weak intra-molecular vibrational modes that may not be detected by
infrared spectroscopy.
12. The apparatus of claim 10, wherein the THz spectroscopic
analysis detects two dimensional THz absorption properties.
13. The apparatus of claim 10, wherein the THz spectroscopic
analysis scans the sample in two dimensions a plurality of times,
each of the scans being scaled with sample size.
14. The apparatus of claim 1, wherein the plurality of
spectroscopic units further comprises: a first spectroscopic unit
for receiving the light beam that has passed though the sample and
performing an orbital angular momentum (OAM) spectroscopic analysis
to generate an OAM parameter output signal a second spectroscopic
unit for receiving the light beam that has passed through the
sample and performing Raman spectroscopy analysis to generate a
Raman parameter output signal; a third spectroscopic unit for
receiving the light beam and performing polarized Raman
spectroscopy analysis and generating a third output signal; a forth
spectroscopic unit for receiving the light beam and performing
non-polarized Raman spectroscopy analysis and generating a fourth
output signal; and wherein the Raman spectroscopy analysis of the
second spectroscopic unit further detects optical vortices within
the received light beam.
15. A method for detecting a material within a sample, comprising:
directing at least one light beam through the sample; receiving the
light beam that has passed through the sample at a plurality of
spectroscopic units; performing a spectroscopic analysis of the
sample based on the received light beam at each of the plurality of
spectroscopic units by analyzing a different parameter with respect
to the sample; providing a separate output signal with respect to
the analysis at each of the plurality of spectroscopic units; and
detecting the material within the sample with respect each of the
provided separate output signals.
16. The method of claim 15, wherein the step of performing further
comprises: performing a polarization wave analysis to generate a
polarization parameter output signal; performing a wavelength
analysis to generate a wavelength parameter output signal; and
performing an orbital angular momentum (OAM) spectroscopic analysis
to generate an OAM parameter output signal.
17. The method of claim 16, wherein the step of performing further
comprises: performing Raman spectroscopy analysis to generate a
Raman parameter output signal; performing infrared spectroscopy
analysis to generate a infrared parameter output signal; performing
an orbital angular momentum (OAM) spectroscopic analysis to
generate an OAM parameter output signal; and performing a
polarization wave analysis to generate a polarization parameter
output signal.
18. The method of claim 15, wherein step of performing further
comprises performing dual comb spectroscopic analysis to generate
an output signal.
19. The method of claim 15, wherein the step of performing further
comprises: performing Raman sideband spectroscopy analysis to
generate a first output signal; performing colloidal particles
manipulation using OAM tweezers; and wherein the light beam
comprises an OAM endowed light beam.
20. The method of claim 15, wherein the step of performing further
comprises: performing OAM spectroscopic analysis that detects
delocalized OAM associated with an envelope wavefunction in a Bloch
framework; and performing OAM spectroscopic analysis that detects
local OAM associated with atoms within the sample.
21. The method of claim 15, wherein the step of performing further
comprises: performing a polarization wave analysis to generate a
polarization parameter output signal; performing an orbital angular
momentum (OAM) spectroscopic analysis to generate an OAM parameter
output signal; further wherein the step of detecting further
comprises detecting a unique signature for the material within the
sample indicated by the polarization parameter output signal and
the OAM parameter output signal.
22. The method of claim 15, wherein the step of performing further
comprises: performing an orbital angular momentum (OAM)
spectroscopic analysis to generate an OAM parameter output signal;
and performing fluorescence spectroscopic analysis to detect
emission spectra and excitation spectra within the sample and
generate a fluorescence parameter output signal.
23. The method of claim 22, wherein the step of performing the
fluorescence spectroscopic analysis further comprises: holding the
exciting radiation at a fixed wavelength; and measuring the emitted
fluorescent intensity as a function of emission wavelength.
24. The method of claim 15, wherein the step of performing further
comprises: performing an orbital angular momentum (OAM)
spectroscopic analysis to generate an OAM parameter output signal;
and performing terahertz (THz) spectroscopic analysis to generate a
fluorescence parameter output signal.
25. The method of claim 24, wherein the step of performing THz
spectroscopic analysis further comprises providing selective
detection of weak inter-molecular and weak intra-molecular
vibrational modes that may not be detected by infrared
spectroscopy.
26. The method of claim 24, wherein the step of performing THz
spectroscopic analysis further comprises detecting two dimensional
THz absorption properties.
27. The method of claim 24, wherein the step of performing THz
spectroscopic analysis further comprises scanning the sample in two
dimensions a plurality of times, each of the scans being scaled
with sample size.
28. The method of claim 15, wherein the step of performing further
comprises: performing an orbital angular momentum (OAM)
spectroscopic analysis to generate an OAM parameter output signal
performing Raman spectroscopy analysis to generate a Raman
parameter output signal and detecting optical vortices within the
received light beam; performing polarized Raman spectroscopy
analysis and generating a third output signal; and performing
non-polarized Raman spectroscopy analysis and generating a fourth
output signal.
29. An apparatus for detecting a material within a sample,
comprising: a light emitting unit for directing at least one light
beam through the sample; a first spectroscopic unit for receiving
the at least one light beam that has passed though the sample and
performing an orbital angular momentum (OAM) spectroscopic analysis
to generate an OAM parameter output signal; at least one second
spectroscopic unit for receiving the at least one light beam that
has passed through the sample and performing a spectroscopic
analysis of the sample based on the received at least one light
beam, each of the at least one spectroscopic unit analyzing a
parameter other than orbital angular momentum and providing a
separate output signal with respect to the analysis; and a
processor for detecting the material with respect to the OAM
parameter output signal and each of the provided separate output
signals.
30. A method for detecting a material within a sample, comprising:
directing at least one light beam through the sample; receiving the
light beam that has passed through the sample at a plurality of
spectroscopic units; performing an orbital angular momentum (OAM)
spectroscopic analysis; generating an OAM parameter output signal
responsive to the OAM spectroscopic analysis; performing at least
one spectroscopic analysis of the sample based on the received at
least one light beam, each of the at least one spectroscopic
analysis analyzing a parameter other than orbital angular momentum;
providing a separate output signal with respect to the
spectroscopic analysis at each of the plurality of spectroscopic
units; and detecting the material within the sample with respect
each of the provided separate output signals.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional
Application No. 62/278,186, filed Jan. 13, 2016, entitled
MULTI-PARAMETER SPECTROSCOPY (Atty. Dkt. No. NXGN-32968), U.S.
Provisional Application No. 62/322,507, filed Apr. 14, 2016,
entitled RAMAN SPECTROSCOPY WITH ORBITAL ANGULAR MOMENTUM (Atty.
Dkt. No. NXGN-33094), U.S. Provisional Application No. 62/365,486,
entitled INCE-GAUSSIAN SPECTROSCOPY (Atty. Dkt. No. NXGN-33217),
and U.S. Provisional Application No. 62/081,846, filed on Nov. 19,
2014, entitled DISTINCT SIGNATURES FOR CONCENTRATION MEASUREMENTS
(Atty. Dkt. No. NXGN-32424), which is incorporated by reference
herein in its entirety.
[0002] This application is also a Continuation-in-Part of U.S.
application Ser. No. 14/339,836, filed on Jul. 24, 2014, entitled
SYSTEM AND METHOD FOR MAKING CONCENTRATION MEASUREMENTS WITHIN A
SAMPLE MATERIAL USING ORBITAL ANGULAR MOMENTUM (Atty. Dkt. No.
NXGN-32196), which published on Sep. 17, 2015, as U.S. Application
Publication No. 2015-0260650. This application is also a
Continuation-in-Part of U.S. application Ser. No. 14/875,507, filed
on Oct. 5, 2015, entitled SYSTEM AND METHOD FOR EARLY DETECTION OF
ALZHEIMERS BY DETECTING AMYLOID-BETA USING ORBITAL ANGULAR MOMENTUM
(Atty. Dkt. No. NXGN-32776.). U.S. application Ser. Nos. 14/339,836
and 14/875,507, and U.S. Application Publication No. 2015-0260650
are incorporated by reference in their entirety.
TECHNICAL FIELD
[0003] The present invention relates to the detection of materials
within a sample, and more particularly, to the detection of
materials within a sample based multi-parameter spectroscopy.
BACKGROUND
[0004] Concentration measurements and detection of the presence of
organic and non-organic materials is of great interest in a number
of applications. In one example, detection of materials within
human tissue is an increasingly important aspect of healthcare for
individuals. The development of non-invasive measurement techniques
for monitoring biological and metabolic agents within human tissue
is an important aspect of diagnosis therapy of various human
diseases and may play a key role in the proper management of
diseases. The development of non-invasive measurement techniques
for monitoring biological and metabolic agents within human tissue
is an important aspect of diagnosis therapy of various human
diseases and may play a key role in the proper management of
diseases. One such material relevant to Alzheimer's is
amyloid-beta. Thus, there is a need for an improved manner of
amyloid-beta detection to better improve detection of early stages
of Alzheimer's.
[0005] Another example of a biological agent that may be monitored
for within human tissue is glucose. Glucose
(C.sub.6H.sub.12O.sub.6) is a monosaccharide sugar and is one of
the most important carbohydrate nutrient sources. Glucose is
fundamental to almost all biological processes and is required for
the production of ATP adenosine triphosphate and other essential
cellular components. The normal range of glucose concentration
within human blood is 70-160 mg/dl depending on the time of the
last meal, the extent of physical tolerance and other factors.
Freely circulating glucose molecules stimulate the release of
insulin from the pancreas. Insulin helps glucose molecules to
penetrate the cell wall by binding two specific receptors within
cell membranes which are normally impermeable to glucose.
[0006] One disease associated with issues related to glucose
concentrations is diabetes. Diabetes is a disorder caused by the
decreased production of insulin, or by a decreased ability to
utilize insulin and transport the glucose across cell membranes. As
a result, a high potentially dangerous concentration of glucose can
accumulate within the blood (hyperglycemia) during the disease.
Therefore, it is of great importance to maintain blood glucose
concentration within a normal range in order to prevent possible
severe physiological complications.
[0007] One significant role of physiological glucose monitoring is
the diagnosis and management of several metabolic diseases, such as
diabetes mellitus (or simply diabetes). There are a number of
invasive and non-invasive techniques presently used for glucose
monitoring. The problem with existing non-invasive glucose
monitoring techniques is that a clinically acceptable process has
not yet been determined. Standard techniques from the analysis of
blood currently involve an individual puncturing a finger and
subsequent analysis of collected blood samples from the finger. In
recent decades, non-invasive blood glucose monitoring has become an
increasingly important topic of investigation in the realm of
biomedical engineering. In particular, the introduction of optical
approaches has caused some advances within the field. Advances in
optics have led to a focused interest in optical imaging
technologies and the development of non-invasive imaging systems.
The application of optical methods to monitoring in cancer
diagnostics and treatment is also a growing field due to the
simplicity and low risk of optical detection methods. In addition
to the medical field, the detection of various types of materials
in a variety of other environments would be readily apparent.
[0008] Many optical techniques for sensing different tissue
metabolites and glucose in living tissue have been in development
over the last 50 years. These methods have been based upon
florescent, near infrared and mid-infrared spectroscopy, Raman
spectroscopy, photoacoustics, optical coherence tomography and
other techniques. However, none of these techniques that have been
tried have proved completely satisfactory.
[0009] Another organic component lending itself to optical material
concentration sensing involves is human skin. The defense
mechanisms of human skin are based on the action of antioxidant
substances such as carotenoids, vitamins and enzymes. Beta carotene
and lycopene represent more than 70% of the carotenoids in the
human organism. The topical or systematic application of beta
carotene and lycopene is a general strategy for improving the
defense system of the human body. The evaluation and optimization
of this treatment requires the measurement of the b-carotene and
lycopene concentrations in human tissue, especially in the human
skin as the barrier to the environment.
[0010] Thus, an improved non-invasive technique enabling the
detection of concentrations and presence of various materials
within a human body or other types of samples would have a number
of applications within the medical field.
SUMMARY
[0011] The present invention, as disclosed and described herein, in
one aspect thereof, comprise an apparatus for detecting a material
within a sample includes a light emitting unit for directing at
least one light beam through the sample. A plurality of
spectroscopic units receive the light beam that has passed through
the sample and performs a spectroscopic analysis of the sample
based on the received light beam. Each of the plurality of
spectroscopic units analyze a different parameter with respect to
the sample, provide a separate output signal with respect to the
analysis. A processor detects the material with respect each of the
provided separate output signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding, reference is now made to
the following description taken in conjunction with the
accompanying drawings in which:
[0013] FIG. 1 illustrates the manner for using an Orbital Angular
Momentum signature to detect the presence of a material within a
sample;
[0014] FIG. 2 illustrates the manner in which an OAM generator
generates an OAM twisted beam;
[0015] FIG. 3 illustrates a light beam having orbital angular
momentum imparted thereto;
[0016] FIG. 4 illustrates a series of parallel wavefronts;
[0017] FIG. 5 illustrates a wavefront having a Poynting vector
spiraling around a direction of propagation of the wavefront;
[0018] FIG. 6 illustrates a plane wavefront;
[0019] FIG. 7 illustrates a helical wavefront;
[0020] FIG. 8 illustrates a plane wave having only variations in
the spin vector;
[0021] FIG. 9 illustrates the application of a unique orbital
angular momentum to a wave;
[0022] FIGS. 10A-10C illustrate the differences between signals
having different orbital angular momentum applied thereto;
[0023] FIG. 11A illustrates the propagation of Poynting vectors for
various eigenmodes;
[0024] FIG. 11B illustrates a spiral phase plate;
[0025] FIG. 12 illustrates a block diagram of an apparatus for
providing concentration measurements and presence detection of
various materials using orbital angular momentum;
[0026] FIG. 13 illustrates an emitter of the system of FIG. 11;
[0027] FIG. 14 illustrates a fixed orbital angular momentum
generator of the system of FIG. 11;
[0028] FIGS. 15A-15D illustrate various holograms for use in
applying an orbital angular momentum to a plane wave signal;
[0029] FIG. 16 illustrates the relationship between
Hermite-Gaussian modes and Laguerre-Gaussian modes;
[0030] FIG. 17 illustrates super-imposed holograms for applying
orbital angular momentum to a signal;
[0031] FIG. 18 illustrates a tunable orbital angular momentum
generator for use in the system of FIG. 11;
[0032] FIG. 19 illustrates a block diagram of a tunable orbital
angular momentum generator including multiple hologram images
therein;
[0033] FIG. 20 illustrates the manner in which the output of the
OAM generator may be varied by applying different orbital angular
momentums thereto;
[0034] FIG. 21 illustrates an alternative manner in which the OAM
generator may convert a Hermite-Gaussian beam to a
Laguerre-Gaussian beam;
[0035] FIG. 22 illustrates the manner in which holograms within an
OAM generator may twist a beam of light;
[0036] FIG. 23 illustrates the manner in which a sample receives an
OAM twisted wave and provides an output wave having a particular
OAM signature;
[0037] FIG. 24 illustrates the manner in which orbital angular
momentum interacts with a molecule around its beam axis;
[0038] FIG. 25 illustrates a block diagram of the matching
circuitry for amplifying a received orbital angular momentum
signal;
[0039] FIG. 26 illustrates the manner in which the matching module
may use non-linear crystals in order to generate a higher order
orbital angular momentum light beam;
[0040] FIG. 27 illustrates a block diagram of an orbital angular
momentum detector and user interface;
[0041] FIG. 28 illustrates the effect of sample concentrations upon
the spin angular polarization and orbital angular polarization of a
light beam passing through a sample;
[0042] FIG. 29 more particularly illustrates the process that
alters the orbital angular momentum polarization of a light beam
passing through a sample;
[0043] FIG. 30 provides a block diagram of a user interface of the
system of FIG. 12;
[0044] FIG. 31 illustrates a network configuration for passing
around data collected via devices such as that illustrated in FIG.
15;
[0045] FIG. 32 provides a block diagram of a more particular
embodiment of an apparatus for measuring the concentration and
presence of glucose using orbital angular momentum;
[0046] FIG. 33 illustrates an optical system for detecting a unique
OAM signature of a signal passing through a sample under test;
[0047] FIG. 34 illustrates the manner in which the ellipticity of
an OAM intensity diagram changes after passing through a
sample;
[0048] FIG. 35 illustrates the manner in which a center of gravity
of an intensity diagram shifts after passing through a sample;
[0049] FIG. 36 illustrates the manner in which an axis of the
intensity diagram shifts after passing through a sample;
[0050] FIG. 37A illustrates an OAM signature of a sample consisting
only of water;
[0051] FIG. 37B illustrates an OAM signature of a sample of 15%
glucose in water;
[0052] FIG. 38A illustrates an interferogram of a sample consisting
only of water;
[0053] FIG. 38B illustrates an interferogram of a sample of 15%
glucose in water;
[0054] FIG. 39 shows the amplitude of an OAM beam;
[0055] FIG. 40 shows the phase of an OAM beam;
[0056] FIG. 41 is a chart illustrating the ellipticity of a beam on
the output of a Cuvette for three different OAM modes;
[0057] FIGS. 42A-42C illustrates the propagation due to and annulus
shaped beam for a Cuvette, water and glucose;
[0058] FIG. 43 illustrates OAM propagation through water for
differing drive voltages;
[0059] FIG. 44 illustrates an example of a light beam that is
altered by a hologram to produce an OAM twisted beam;
[0060] FIG. 45 illustrates various OAM modes produced by a spatial
light modulator;
[0061] FIG. 46 illustrates an ellipse;
[0062] FIG. 47 is a flow diagram illustrating a process for
analyzing intensity images;
[0063] FIG. 48 illustrates an ellipse fitting algorithm;
[0064] FIG. 49 illustrates the generation of fractional orthogonal
states;
[0065] FIG. 50 illustrates the use of a spatial light modulator for
the generation of fractional OAM beams;
[0066] FIG. 51 illustrates one manner for the generation of
fractional OAM beam using superimposed Laguerre Gaussian beams;
[0067] FIG. 52 illustrates the decomposition of a fractional OAM
beam into integer OAM states;
[0068] FIG. 53 illustrates the manner in which a spatial light
modulator may generate a hologram for providing fractional OAM
beams;
[0069] FIG. 54 illustrates the generation of a hologram to produce
non-integer OAM beams;
[0070] FIG. 55 is a flow diagram illustrating the generation of a
hologram for producing non-integer OAM beams;
[0071] FIG. 56 illustrates the intensity and phase profiles for
noninteger OAM beams;
[0072] FIG. 57 is a block diagram illustrating fractional OAM beams
for OAM spectroscopy analysis;
[0073] FIG. 58 illustrates an example of an OAM state profile;
[0074] FIG. 59 illustrates the manner for combining multiple varied
spectroscopy techniques to provide multiparameter spectroscopy
analysis;
[0075] FIG. 60 illustrates a schematic drawing of a spec parameter
for making relative measurements in an optical spectrum;
[0076] FIG. 61 illustrates an electromagnetic spectrum;
[0077] FIG. 62 illustrates the infrared spectrum of water
vapor;
[0078] FIG. 63 illustrates the stretching and bending vibrational
modes of water;
[0079] FIG. 64 illustrates the stretching and bending vibrational
modes for CO.sub.2;
[0080] FIG. 65 illustrates the infrared spectrum of carbon
dioxide;
[0081] FIG. 66 illustrates the energy of an anharmonic oscillator
as a function of the interatomic distance;
[0082] FIG. 67 illustrates the energy curve for a vibrating spring
and quantized energy level;
[0083] FIG. 68 illustrates Rayleigh scattering and Ramen scattering
by Stokes and anti-Stokes resonance;
[0084] FIG. 69 illustrates circuits for carrying out polarized
Rahman techniques;
[0085] FIG. 70 illustrates circuitry for combining polarized and
non-polarized Rahman spectroscopy;
[0086] FIG. 71 illustrates a combination of polarized and
non-polarized Rahman spectroscopy with optical vortices;
[0087] FIG. 72 illustrates the electromagnetic wave attenuation by
atmospheric water versus frequency and wavelength;
[0088] FIG. 73 illustrates the absorption and emission sequences
associated with fluorescence spectroscopy;
[0089] FIG. 74A illustrates the absorption spectra of various
materials;
[0090] FIG. 74B illustrates the fluorescence spectra of various
materials;
[0091] FIG. 75 illustrates a pump-probe spectroscopy set up;
[0092] FIG. 76 illustrates an enhanced Ramen signal;
[0093] FIG. 77 illustrates a pump-probe OAM spectroscopy set
up;
[0094] FIG. 78 illustrates measured eccentricities of OAM
beams;
[0095] FIG. 79 illustrates a combination of OAM spectroscopy with
Ramen spectroscopy for the generation of differential signals;
[0096] FIG. 80 illustrates a flow diagram of an alignment
procedure
[0097] FIG. 81 illustrates a balanced detection scheme;
[0098] FIG. 82 illustrates an elliptical coordinate system;
[0099] FIG. 83 illustrates a tracing the lips with constant
[0100] FIG. 84 illustrates tracing hyperbolas with constant
[0101] FIGS. 85A and 85B illustrates even Ince Polynomials;
[0102] FIG. 86 illustrates modes and phases for even Ince mode;
[0103] FIGS. 87A and 87B illustrates odd Ince Polynomials;
[0104] FIG. 88 illustrates modes and phases for odd Ince mode;
[0105] FIG. 89 illustrates dual comp spectroscopy; and
[0106] FIG. 90 illustrates a wearable multi-parameter spectroscopy
device.
DETAILED DESCRIPTION
[0107] Referring now to the drawings, wherein like reference
numbers are used herein to designate like elements throughout, the
various views and embodiments of a system and method for detecting
materials using orbital angular momentum signatures are illustrated
and described, and other possible embodiments are described. The
figures are not necessarily drawn to scale, and in some instances
the drawings have been exaggerated and/or simplified in places for
illustrative purposes only. One of ordinary skill in the art will
appreciate the many possible applications and variations based on
the following examples of possible embodiments.
[0108] Referring now to the drawings, and more particularly to FIG.
1, there is illustrated the manner for detecting the presence of a
particular material within a sample based upon the unique orbital
angular momentum signature imparted to a signal passing through the
sample. An optical signal 102 having a series of plane waves
therein is applied to a device for applying an orbital angular
momentum (OAM) signal to the optical signal 102 such as a spatial
light modulator (SLM) 104. While the present embodiment envisions
the use of an optical signal 102, other types of signals having
orbital angular momentum or other orthogonal signals therein may be
utilized in alternative embodiments. The SLM 104 generates an
output signal 106 having a known OAM twist applied to the signal.
The OAM twist has known characteristics that act as a baseline
prior to the application of the output signal 106 to a sample 108.
The sample 108 may comprise a material contained within a holding
container, such as a cuvette, or may be a material in its natural
state, such as the eye or body of a patient or its naturally
occurring location in nature. The sample 108 only indicates that a
particular material or item of interest is being detected by the
describe system. While passing through the sample 108, the output
signal 106 has a unique OAM signature applied thereto that is
provided as an OAM distinct signature signal 110. OAM beams have
been observed to exhibit unique topological evolution upon
interacting with chiral solutions. While it has been seen that
chiral molecules create unique OAM signatures when an OAM beam is
passed through a sample of the chiral material, the generation of
unique OAM signatures from signals passing through non-chiral
molecules/material may also be provided. Given these unique
topological features one can detect the existence of a molecule in
a given solution with specific signatures in both the amplitude and
phase measurements. This distinct signature signal 110 may then be
examined using for example a camera 112 in order to detect the
unique signal characteristics applied thereto and determine the
material within the sample based upon this unique signature.
Application of multi-parameter spectroscopy for the detection of
different molecules can be applied to different industries
including, but not limited to, food (identification of food
spoilage), Nanoscale Material development for defense and national
security, chemical industries, pharma and medical industries for
testing where non-invasive solutions are critical, medical and
dental industry for identification of infections, cancer cells,
organic compounds and many others. The determination of the
particular material indicated by the unique signature may be
determined in one embodiment by comparison of the signature to a
unique database of signatures that include known signatures that
are associated with a particular material or concentration. The
manner of creating such a database would be known to one skilled in
the art.
[0109] Referring now to FIG. 2 illustrates the manner in which an
OAM generator 220 may generate an OAM twisted beam 222. The OAM
generator 210 may use any number of devices to generate the twisted
beam 222 including holograms with an amplitude mask, holograms with
a phase mask, Spatial Light Modulators (SLMs) or Digital Light
Processors (DLPs). The OAM generator 220 receives a light beam 221
(for example from a laser) that includes a series of plane waves.
The OAM generator 220 applies an orbital angular momentum to the
beam 222. The beam 222 includes a single OAM mode as illustrated by
the intensity diagram 223. The OAM twisted beam 222 is passed
through a sample 224 including material that is being detected. As
mentioned previously the sample 224 may be in a container or its
naturally occurring location. The presence of the material within
the sample 224 will create new OAM mode levels within the intensity
diagram 225. Once the beam 222 passes through the sample 224, the
output beam 226 will have three distinct signatures associated
therewith based on a detection of a particular material at a
particular concentration. These signatures include a change in
eccentricity 228 of the intensity pattern, a shift or translation
230 in the center of gravity of the intensity pattern and a
rotation 232 in three general directions (.alpha., .beta., .gamma.)
of the ellipsoidal intensity pattern output. Each of these distinct
signature indications may occur in any configuration and each
distinct signature will provide a unique indication of the presence
of particular materials and the concentrations of these detected
materials. These three distinct signatures will appear when a
molecule under measurement is detected and the manner of change of
these signatures represents concentration levels. The detection of
the helicity spectrums from the beam passing through the sample 224
involves detecting the helical wave scatters (forward and backward)
from the sample material.
[0110] The use of the OAM of light for the metrology of glucose,
amyloid beta and other chiral materials has been demonstrated using
the above-described configurations. OAM beams are observed to
exhibit unique topological evolution upon interacting with chiral
solutions within 3 cm optical path links. It should be realized
that unique topological evolution may also be provided from
non-chiral materials. Chiral solution, such as Amyloid-beta,
glucose and others, have been observed to cause orbital angular
momentum (OAM) beams to exhibit unique topological evolution when
interacting therewith. OAM is not typically carried by naturally
scattered photons which make use of the twisted beams more accurate
when identifying the helicities of chiral molecules because OAM
does not have ambient light scattering (noise) in its detection.
Thus, the unique OAM signatures imparted by a material is not
interfered with by ambient light scattering (noise) that does not
carry OAM in naturally scattered photons making detection much more
accurate. Given these unique topological features one can detect
the amyloid-beta presence and concentration within a given sample
based upon a specific signature in both amplitude and phase
measurements. Molecular chirality signifies a structural handedness
associated with variance under spatial inversion or a combination
of inversion and rotation, equivalent to the usual criteria of a
lack of any proper axes of rotation. Something is chiral when
something cannot be made identical to its reflection. Chiral
molecules that are not superimposable on their mirror image are
known as Enantiomers. Traditionally, engages circularly polarized
light, even in the case of optical rotation, interpretation of the
phenomenon commonly requires the plane polarized state to be
understood as a superposition of circular polarizations with
opposite handedness. For circularly polarized light, the left and
right forms designate the sign of intrinsic spin angular momentum,
.+-.h and also the helicity of the locus described by the
associated electromagnetic field vectors. For this reason its
interactions with matter are enantiomerically specific.
[0111] The continuous symmetry measure (CSM) is used to evaluate
the degree of symmetry of a molecule, or the chirality. This value
ranges from 0 to 100. The higher the symmetry value of a molecule
the more symmetry distorted the molecule and the more chiral the
molecule. The measurement is based on the minimal distance between
the chiral molecule and the nearest achiral molecule.
[0112] The continuous symmetry measure may be achieved according to
the equation:
S ( G ) = 100 .times. min 1 Nd 2 k = 1 N Q k - Q ^ k 2 ##EQU00001##
[0113] Q.sub.k: The original structure [0114] {circumflex over
(Q)}.sub.k: The symmetry-operated structure [0115] N: Number of
vertices [0116] d: Size normalization factor [0117] *The scale is
0-1 (0-100): [0118] The larger S(G) is, the higher is the deviation
from G-symmetry
[0119] SG as a continuous chirality measure may be determined
according to:
S ( G ) = 100 .times. min 1 Nd 2 k = 1 N Q k - Q ^ k 2 ##EQU00002##
[0120] G: The achiral symmetry point group which minimizes S(G)
[0121] Achiral molecule: S(G)=0
[0122] An achiral molecule has a value of S(G)=0. The more chiral a
molecule is the higher the value of S(G).
[0123] The considerable interest in orbital angular momentum has
been enhanced through realization of the possibility to engineer
optical vortices. Here, helicity is present in the wave-front
surface of the electromagnetic fields and the associated angular
momentum is termed "orbital". The radiation itself is commonly
referred to as a `twisted` or `helical` beam. Mostly, optical
vortices have been studied only in their interactions with achiral
matter--the only apparent exception is some recent work on liquid
crystals. It is timely and of interest to assess what new features,
if any, can be expected if such beams are used to interrogate any
system whose optical response is associated with enantiomerically
specific molecules.
[0124] First the criteria for manifestations of chirality in
optical interactions are constructed in generalized form. For
simplicity, materials with a unique enantiomeric specificity are
assumed--signifying a chirality that is intrinsic and common to all
molecular components (or chromophores) involved in the optical
response. Results for systems of this kind will also apply to
single molecule studies. Longer range translation/rotation order
can also produce chirality, as for example in twisted nematic
crystals, but such mesoscopic chirality cannot directly engender
enantiomerically specific interactions. The only exception is where
optical waves probe two or more electronically distinct,
dissymmetrically oriented but intrinsically achiral molecules or
chromophores.
[0125] Chiroptical interactions can be distinguished by their
electromagnetic origins: for molecular systems in their usual
singlet electronic ground state, they involve the spatial variation
of the electric and magnetic fields associated with the input of
optical radiation. This variation over space can be understood to
engage chirality either through its coupling with di-symmetrically
placed, neighboring chromophore groups (Kirkwood's two-group model,
of limited application) or more generally through the coupling of
its associated electric and magnetic fields with individual groups.
As chirality signifies a local breaking of parity it permits an
interference of electric and magnetic interactions. Even in the two
group case, the paired electric interactions of the system
correspond to electric and magnetic interactions of the single
entity which the two groups comprise. Thus, for convenience, the
term `chiral center` is used in the following to denote either
chromophore or molecule.
[0126] With the advent of the laser, the Gaussian beam solution to
the wave equation came into common engineering parlance, and its
extension two higher order laser modes, Hermite Gaussian for
Cartesian symmetry; Laguerre Gaussian for cylindrical symmetry,
etc., entered laboratory optics operations. Higher order Laguerre
Gaussian beam modes exhibit spiral, or helical phase fronts. Thus,
the propagation vector, or the eikonal of the beam, and hence the
beams momentum, includes in addition to a spin angular momentum, an
orbital angular momentum, i.e. a wobble around the sea axis. This
phenomenon is often referred to as vorticity. The expression for a
Laguerre Gaussian beam is given in cylindrical coordinates:
u ( r , .theta. , z ) = 2 pl 1 + .delta. 0 , m .pi. ( m + p ) ! 1 w
( z ) exp [ j ( 2 p + m + 1 ) ( .psi. ( z ) - .psi. 0 ) ] ( 2 r w (
z ) ) L p m ( 2 r 2 w ( z ) 2 ) exp [ - j k r 2 2 q ( z ) + im
.theta. ] ##EQU00003##
[0127] Here, w (x) is the beam spot size, q(c) is the complex beam
parameter comprising the evolution of the spherical wave front and
the spot size. Integers p and m are the radial and azimuthal modes,
respectively. The exp(im.theta.) term describes the spiral phase
fronts.
[0128] Referring now also to FIG. 3, there is illustrated one
embodiment of a beam for use with the system. A light beam 300
consists of a stream of photons 302 within the light beam 300. Each
photon has an energy .+-..omega. and a linear momentum of .+-.k
which is directed along the light beam axis 304 perpendicular to
the wavefront. Independent of the frequency, each photon 302 within
the light beam has a spin angular momentum 306 of .+-. aligned
parallel or antiparallel to the direction of light beam
propagation. Alignment of all of the photons 302 spins gives rise
to a circularly polarized light beam. In addition to the circular
polarization, the light beams also may carry an orbital angular
momentum 308 which does not depend on the circular polarization and
thus is not related to photon spin.
[0129] Lasers are widely used in optical experiments as the source
of well-behaved light beams of a defined frequency. A laser may be
used for providing the light beam 300. The energy flux in any light
beam 300 is given by the Poynting vector which may be calculated
from the vector product of the electric and magnetic fields within
the light beam. In a vacuum or any isotropic material, the Poynting
vector is parallel to the wave vector and perpendicular to the
wavefront of the light beam. In a normal laser light, the
wavefronts 400 are parallel as illustrated in FIG. 4. The wave
vector and linear momentum of the photons are directed along the
axis in a z direction 402. The field distributions of such light
beams are paraxial solutions to Maxwell's wave equation but
although these simple beams are the most common, other
possibilities exist.
[0130] For example, beams that have l intertwined helical fronts
are also solutions of the wave equation. The structure of these
complicated beams is difficult to visualize, but their form is
familiar from the l=3 fusilli pasta. Most importantly, the
wavefront has a Poynting vector and a wave vector that spirals
around the light beam axis direction of propagation as illustrated
in FIG. 5 at 502.
[0131] A Poynting vector has an azimuthal component on the wave
front and a non-zero resultant when integrated over the beam
cross-section. The spin angular momentum of circularly polarized
light may be interpreted in a similar way. A beam with a circularly
polarized planer wave front, even though it has no orbital angular
momentum, has an azimuthal component of the Poynting vector
proportional to the radial intensity gradient. This integrates over
the cross-section of the light beam to a finite value. When the
beam is linearly polarized, there is no azimuthal component to the
Poynting vector and thus no spin angular momentum.
[0132] Thus, the momentum of each photon 302 within the light beam
300 has an azimuthal component. A detailed calculation of the
momentum involves all of the electric fields and magnetic fields
within the light beam, particularly those electric and magnetic
fields in the direction of propagation of the beam. For points
within the beam, the ratio between the azimuthal components and the
z components of the momentum is found to be l/kr. (where l=the
helicity or orbital angular momentum; k=wave number 2.pi./.lamda.;
r=the radius vector.) The linear momentum of each photon 302 within
the light beam 300 is given by k, so if we take the cross product
of the azimuthal component within a radius vector, r, we obtain an
orbital momentum for a photon 602 of l. Note also that the
azimuthal component of the wave vectors is l/r and independent of
the wavelength.
[0133] Referring now to FIGS. 6 and 7, there are illustrated plane
wavefronts and helical wavefronts. Ordinarily, laser beams with
plane wavefronts 602 are characterized in terms of Hermite-Gaussian
modes. These modes have a rectangular symmetry and are described by
two mode indices m 604 and n 606. There are m nodes in the x
direction and n nodes in the y direction. Together, the combined
modes in the x and y direction are labeled HG.sub.mn 608. In
contrast, as shown in FIG. 7, beams with helical wavefronts 702 are
best characterized in terms of Laguerre-Gaussian modes which are
described by indices I 703, the number of intertwined helices 704,
and p, the number of radial nodes 706. The Laguerre-Gaussian modes
are labeled LG.sub.mn 710. For l.noteq.0, the phase singularity on
a light beam 300 results in 0 on axis intensity. When a light beam
300 with a helical wavefront is also circularly polarized, the
angular momentum has orbital and spin components, and the total
angular momentum of the light beam is (l.+-.) per photon.
[0134] Using the orbital angular momentum state of the transmitted
energy signals, physical information can be embedded within the
electromagnetic radiation transmitted by the signals. The
Maxwell-Heaviside equations can be represented as:
.gradient. E = .rho. 0 ##EQU00004## .gradient. .times. E = -
.differential. B .differential. t ##EQU00004.2## .gradient. B = 0
##EQU00004.3## .gradient. .times. B = 0 .mu. 0 .differential. E
.differential. t + .mu. 0 j ( t , x ) the ##EQU00004.4##
where .gradient. is the del operator, E is the electric field
intensity and B is the magnetic flux density. Using these
equations, we can derive 23 symmetries/conserve quantities from
Maxwell's original equations. However, there are only ten
well-known conserve quantities and only a few of these are
commercially used. Historically if Maxwell's equations where kept
in their original quaternion forms, it would have been easier to
see the symmetries/conserved quantities, but when they were
modified to their present vectorial form by Heaviside, it became
more difficult to see such inherent symmetries in Maxwell's
equations.
[0135] The conserved quantities and the electromagnetic field can
be represented according to the conservation of system energy and
the conservation of system linear momentum. Time symmetry, i.e. the
conservation of system energy can be represented using Poynting's
theorem according to the equations:
H = i m i .gamma. i c 2 + 0 2 .intg. 3 x ( E 2 + c 2 B 2 )
##EQU00005## U mech t + U em t + s ' 2 x ' n ' ^ S = 0
##EQU00005.2##
[0136] The space symmetry, i.e., the conservation of system linear
momentum representing the electromagnetic Doppler shift can be
represented by the equations:
P = i m i .gamma. i v i + 0 .intg. 3 x ( E .times. B ) ##EQU00006##
p mech t + p em t + s ' 2 x ' n ' ^ T = 0 ##EQU00006.2##
[0137] The conservation of system center of energy is represented
by the equation:
R = 1 H i ( x i = x 0 ) m i .gamma. i c 2 + 0 2 H .intg. 3 x ( x -
x 0 ) ( E 2 + c 2 B 2 ) ##EQU00007##
[0138] Similarly, the conservation of system angular momentum,
which gives rise to the azimuthal Doppler shift is represented by
the equation:
J mech t + J em t + s ' 2 x ' n ' M = 0 ##EQU00008##
[0139] For radiation beams in free space, the EM field angular
momentum J.sup.em can be separated into two parts:
J.sup.em= .sub.0.intg..sub.V'd.sup.3x'(E.times.A)+
.sub.0.intg..sub.V'd.sup.3x'E.sub.i[(x'-x.sub.0).times..gradient.]A.sub.i
[0140] For each singular Fourier mode in real valued
representation:
J em = - 0 2 .omega. .intg. V ' 3 x ' ( E * .times. E ) - 0 2
.omega. .intg. V ' 3 x ' E i [ ( x ' - x 0 ) .times. .gradient. ] E
i ##EQU00009##
[0141] The first part is the EM spin angular momentum S.sup.em, its
classical manifestation is wave polarization. And the second part
is the EM orbital angular momentum L.sup.em its classical
manifestation is wave helicity. In general, both EM linear momentum
P.sup.em, and EM angular momentum J.sup.em=L.sup.em+S.sup.em are
radiated all the way to the far field.
[0142] By using Poynting theorem, the optical vorticity of the
signals may be determined according to the optical velocity
equation:
.differential. U .differential. t + .gradient. S = 0
##EQU00010##
where S is the Poynting vector
S = 1 4 ( E .times. H * + E * .times. H ) ##EQU00011##
and U is the energy density
U = 1 4 ( E 2 + .mu. 0 H 2 ) ##EQU00012##
with E and H comprising the electric field and the magnetic field,
respectively, and and .mu..sub.0 being the permittivity and the
permeability of the medium, respectively. The optical vorticity V
may then be determined by the curl of the optical velocity
according to the equation:
V = .gradient. .times. v opt = .gradient. .times. ( E .times. H * +
E * .times. H E 2 + .mu. 0 H 2 ) ##EQU00013##
[0143] Referring now to FIGS. 8 and 9, there are illustrated the
manner in which a signal and an associated Poynting vector of the
signal vary in a plane wave situation (FIG. 8) where only the spin
vector is altered, and in a situation wherein the spin and orbital
vectors are altered in a manner to cause the Poynting vector to
spiral about the direction of propagation (FIG. 9).
[0144] In the plane wave situation, illustrated in FIG. 8, when
only the spin vector of the plane wave is altered, the transmitted
signal may take on one of three configurations. When the spin
vectors are in the same direction, a linear signal is provided as
illustrated generally at 804. It should be noted that while 804
illustrates the spin vectors being altered only in the x direction
to provide a linear signal, the spin vectors can also be altered in
the y direction to provide a linear signal that appears similar to
that illustrated at 804 but in a perpendicular orientation to the
signal illustrated at 804. In linear polarization such as that
illustrated at 804, the vectors for the signal are in the same
direction and have a same magnitude.
[0145] Within a circular polarization as illustrated at 806, the
signal vectors 812 are 90 degrees to each other but have the same
magnitude. This causes the signal to propagate as illustrated at
806 and provide the circular polarization 814 illustrated in FIG.
8. Within an elliptical polarization 808, the signal vectors 816
are also 90 degrees to each other but have differing magnitudes.
This provides the elliptical polarizations 818 illustrated for the
signal propagation 408. For the plane waves illustrated in FIG. 8,
the Poynting vector is maintained in a constant direction for the
various signal configurations illustrated therein.
[0146] The situation in FIG. 9 illustrates when a unique orbital
angular momentum is applied to a signal. When this occurs, Poynting
vector S 910 will spiral around the general direction of
propagation 912 of the signal. The Poynting vector 910 has three
axial components S.sub..phi., S.sub.p and S.sub.z which vary
causing the vector to spiral about the direction of propagation 912
of the signal. The changing values of the various vectors
comprising the Poynting vector 910 may cause the spiral of the
Poynting vector to be varied in order to enable signals to be
transmitted on a same wavelength or frequency as will be more fully
described herein. Additionally, the values of the orbital angular
momentum indicated by the Poynting vector 910 may be measured to
determine the presence of particular materials and the
concentrations associated with particular materials being processed
by a scanning mechanism.
[0147] FIGS. 10A-10C illustrate the differences in signals having a
different helicity (i.e., orbital angular momentum applied
thereto). The differing helicities would be indicative of differing
materials and concentration of materials within a sample that a
beam was being passed through. By determining the particular
orbital angular momentum signature associated with a signal, the
particular material and concentration amounts of the material could
be determined. Each of the spiraling Poynting vectors associated
with a signal 1002, 1004 and 1006 provides a different-shaped
signal. Signal 1002 has an orbital angular momentum of +1, signal
1004 has an orbital angular momentum of +3 and signal 1006 has an
orbital angular momentum of -4. Each signal has a distinct orbital
angular momentum and associated Poynting vector enabling the signal
to be indicative of a particular material and concentration of
material that is associated with the detected orbital angular
momentum. This allows determinations of materials and
concentrations of various types of materials to be determined from
a signal since the orbital angular momentums are separately
detectable and provide a unique indication of the particular
material and the concentration of the particular material that has
affected the orbital angular momentum of the signal transmitted
through the sample material.
[0148] FIG. 11A illustrates the propagation of Poynting vectors for
various Eigen modes. Each of the rings 1120 represents a different
Eigen mode or twist representing a different orbital angular
momentum. Each of the different orbital angular momentums is
associated with particular material and a particular concentration
of the particular material. Detection of orbital angular momentums
provides an indication of the a presence of an associated material
and a concentration of the material that is being detected by the
apparatus. Each of the rings 1120 represents a different material
and/or concentration of a selected material that is being
monitored. Each of the Eigen modes has a Poynting vector 1122 for
generating the rings indicating different materials and material
concentrations.
[0149] Topological charge may be multiplexed to the frequency for
either linear or circular polarization. In case of linear
polarizations, topological charge would be multiplexed on vertical
and horizontal polarization. In case of circular polarization,
topological charge would multiplex on left hand and right hand
circular polarizations. The topological charge is another name for
the helicity index "I" or the amount of twist or OAM applied to the
signal. The helicity index may be positive or negative.
[0150] The topological charges s can be created using Spiral Phase
Plates (SPPs) as shown in FIG. 11B using a proper material with
specific index of refraction and ability to machine shop or phase
mask, holograms created of new materials. Spiral Phase plates can
transform a RF plane wave (l=0) to a twisted wave of a specific
helicity (i.e. l=+1).
[0151] Referring now to FIG. 12, there is illustrated a block
diagram of the apparatus for providing detection of the presence of
a material and concentration measurements of various materials
responsive to the orbital angular momentum detected by the
apparatus in accordance with the principles described herein above.
An emitter 1202 transmits wave energy 1204 that comprises a series
of plane waves. The emitter 1202 may provide a series of plane
waves such as those describes previously with respect to FIG. 7.
The orbital angular momentum generation circuitry 1206 generates a
series of waves having an orbital angular momentum applied to the
waves 1208 in a known manner. The orbital angular momentum
generation circuitry 1206 may utilize holograms or some other type
of orbital angular momentum generation process as will be more
fully described herein below. The OAM generation circuitry 1206 may
be generated by transmitting plane waves through a spatial light
modulator (SLM), an amplitude mask or a phase mask. The orbital
angular momentum twisted waves 1208 are applied to a sample
material 1210 under test. The sample material 1210 contains a
material, and the presence and concentration of the material is
determined via a detection apparatus in accordance with the process
described herein. The sample material 1210 may be located in a
container or at its naturally occurring location in nature such as
an individual's body.
[0152] A series of output waves 1212 from the sample material 1210
exit the sample and have a particular orbital angular momentum
imparted thereto as a result of the material and the concentration
of the particular material under study within the sample material
1210. The output waves 1212 are applied to a matching module 1214
that includes a mapping aperture for amplifying a particular
orbital angular momentum generated by the specific material under
study. The matching module 1214 will amplify the orbital angular
momentums associated with the particular material and concentration
of material that is detected by the apparatus. The amplified OAM
waves 1216 are provided to a detector 1218. The detector 1218
detects OAM waves relating to the material and the concentration of
a material within the sample and provides this information to a
user interface 1220. The detector 1218 may utilize a camera to
detect distinct topological features from the beam passing through
the sample. The user interface 1220 interprets the information and
provides relevant material type and concentration indication to an
individual or a recording device.
[0153] Referring now to FIG. 13, there is more particularly
illustrated the emitter 1202. The emitter 1202 may emit a number of
types of energy waves 1204 to the OAM generation module 1206. The
emitter 1202 may emit optical waves 1300, electromagnetic waves
1302, acoustic waves 1304 or any other type of particle waves 1306.
The emitted waves 1204 are plane waves such as those illustrated in
FIG. 4 having no orbital angular momentum applied thereto and may
come from a variety of types of emission devices and have
information included therein. In one embodiment, the emission
device may comprise a laser. Plane waves have wavefronts that are
parallel to each other having no twist or helicity applied thereto,
and the orbital angular momentum of the wave is equal to 0. The
Poynting vector within a plane wave is completely in line with the
direction of propagation of the wave.
[0154] The OAM generation module 1206 processes the incoming plane
wave 1204 and imparts a known orbital angular momentum onto the
plane waves 1204 provided from the emitter 1202. The OAM generation
module 1206 generates twisted or helical electromagnetic, optic,
acoustic or other types of particle waves from the plane waves of
the emitter 1202. A helical wave 1208 is not aligned with the
direction of propagation of the wave but has a procession around
direction of propagation as shown in FIG. 14. The OAM generation
module 1206 may comprise in one embodiment a fixed orbital angular
momentum generator 1402 as illustrated in FIG. 14. The fixed
orbital angular momentum generator 1402 receives the plane waves
1204 from the emitter 1202 and generates an output wave 1404 having
a fixed orbital angular momentum applied thereto.
[0155] The fixed orbital angular momentum generator 1402 may in one
embodiment comprise a holographic image for applying the fixed
orbital angular momentum to the plane wave 1204 in order to
generate the OAM twisted wave 1404. Various types of holographic
images may be generated in order to create the desired orbital
angular momentum twist to an optical signal that is being applied
to the orbital angular momentum generator 1402. Various examples of
these holographic images are illustrated in FIG. 15A-15D. In one
embodiment, the conversion of the plane wave signals transmitted
from the emitter 1202 by the orbital angular momentum generation
circuitry 1206 may be achieved using holographic images.
[0156] Most commercial lasers emit an HG.sub.00 (Hermite-Gaussian)
mode 1602 (FIG. 16) with a planar wave front and a transverse
intensity described by a Gaussian function. Although a number of
different methods have been used to successfully transform an
HG.sub.00 Hermite-Gaussian mode 1602 into a Laguerre-Gaussian mode
1604, the simplest to understand is the use of a hologram.
[0157] The cylindrical symmetric solution u.sub.pl (r, .phi., z)
which describes Laguerre-Gaussian beams, is given by the
equation:
u pl ( r , .phi. , z ) = C ( 1 + z 2 / z R 2 ) 1 / 2 [ r 2 w ( z )
] l L p l [ 2 r 2 w 2 ( z ) ] exp [ - r 2 w 2 ( z ) ] exp [ - kr 2
z 2 ( z 2 + z R 2 ) ] exp ( - l .phi. ) .times. exp [ ( 2 p + l + 1
) tan - 1 z z R ] ##EQU00014##
Where z.sub.R is the Rayleigh range, w(z) is the radius of the
beam, L.sub.P is the Laguerre polynomial, C is a constant, and the
beam waist is at z=0.
[0158] In its simplest form, a computer generated hologram is
produced from the calculated interference pattern that results when
the desired beam intersects the beam of a conventional laser at a
small angle. The calculated pattern is transferred to a high
resolution holographic film. When the developed hologram is placed
in the original laser beam, a diffraction pattern results. The
first order of which has a desired amplitude and phase
distribution. This is one manner for implementing the OAM
generation module 1206. A number of examples of holographic images
for use within a OAM generation module are illustrated with respect
to FIGS. 15A-15D.
[0159] There are various levels of sophistication in hologram
design. Holograms that comprise only black and white areas with no
grayscale are referred to as binary holograms. Within binary
holograms, the relative intensities of the two interfering beams
play no role and the transmission of the hologram is set to be zero
for a calculated phase difference between zero and .pi., or unity
for a phase difference between .pi. and 2.pi.. A limitation of
binary holograms is that very little of the incident power ends up
in the first order diffracted spot, although this can be partly
overcome by blazing the grating. When mode purity is of particular
importance, it is also possible to create more sophisticated
holograms where the contrast of the pattern is varied as a function
of radius such that the diffracted beam has the required radial
profile.
[0160] A plane wave shining through the holographic images 1502
will have a predetermined orbital angular momentum shift applied
thereto after passing through the holographic image 1502. OAM
generator 1202 is fixed in the sense that a same image is used and
applied to the beam being passed through the holographic image.
Since the holographic image 1502 does not change, the same orbital
angular momentum is always applied to the beam being passed through
the holographic image 1502. While FIGS. 15A-15D illustrate a number
of embodiments of various holographic images that might be utilized
within the orbital angular momentum generator 1202, it will be
realized that any type of holographic image 1502 may be utilized in
order to achieve the desired orbital angular momentum within an
beam being shined through the image 1502.
[0161] In another example of a holographic image illustrated in
FIG. 17, there is illustrated a hologram that utilizes two separate
holograms that are gridded together to produce a rich number of
orbital angular momentum (l). The superimposed holograms of FIG. 17
have an orbital angular momentum of l=1 and l=3 which are
superimposed upon each other to compose the composite vortex grid
1702. The holograms utilized may also be built in a manner that the
two holograms are gridded together to produce a varied number of
orbital angular momentums (l) not just on a line (l=+1, l=0, l=-1)
but on a square which is able to identify the many variables more
easily. Thus, in the example in FIG. 17, the orbital angular
momentums along the top edge vary from +4 to +1 to -2 and on the
bottom edge from +2 to -1 to -4. Similarly, along the left edge the
orbital angular momentums vary from +4 to +3 to +2 and on the right
edge from -2 to -3 to -4. Across the horizontal center of the
hologram the orbital angular momentums provided vary from +3 to 0
to -3 and along the vertical axis vary from +1 to 0 to -1. Thus,
depending upon the portion of the grid a beam may pass through,
varying orbital angular momentum may be achieved.
[0162] Referring now to FIG. 18, in addition to a fixed orbital
angular momentum generator, the orbital angular momentum generation
circuitry 1206 may also comprise a tunable orbital angular momentum
generator circuitry 1802. The tunable orbital angular momentum
generator 1802 receives the input plane wave 1204 but additionally
receives one or more tuning parameters 1804. The tuning parameters
1804 tune the tunable OAM generator 1802 to apply a selected
orbital angular momentum so that the tuned OAM wave 1806 that is
output from the OAM generator 1802 has a selected orbital angular
momentum value applied thereto.
[0163] This may be achieved in any number of fashions. In one
embodiment, illustrated in FIG. 22, the tunable orbital angular
momentum generator 1802 may include multiple hologram images 2202
within the tunable OAM generator 1802. The tuning parameters 1804
enable selection of one of the holographic images 2206 in order to
provide the desired OAM wave twisted output signal 1806 through a
selector circuit 2204. Alternatively, the gridded holographic image
such as that described in FIG. 16 may be utilized and the beam
shined on a portion of the gridded image to provide the desired OAM
output. The tunable OAM generator 1802 has the advantage of being
controlled to apply a particular orbital angular momentum to the
output orbital angular momentum wave 1806 depending upon the
provided input parameter 1804. This enables the presence and
concentrations of a variety of different materials to be monitored,
or alternatively, for various different concentrations of the same
material to be monitored.
[0164] Referring now to FIG. 19, there is more particularly
implemented a block diagram of a tunable orbital angular momentum
generator 1802. The generator 1802 includes a plurality of
holographic images 1902 for providing orbital angular momentums of
various types to a provided light signal. These holographic images
1902 are selected responsive to a selector circuitry 1904 that is
responsive to the input tuning parameters 1804. The selected filter
1906 comprises the holographic image that has been selected
responsive to the selector controller 1904 and receives the input
plane waves 1204 to provide the tuned orbital angular momentum wave
output 1206. In this manner, signals having a desired orbital
angular momentum may be output from the OAM generation circuitry
1206.
[0165] Referring now to FIG. 20, there is illustrated the manner in
which the output of the OAM generator 1206 may vary a signal by
applying different orbital angular momentums thereto. FIG. 20
illustrates helical phase fronts in which the Poynting vector is no
longer parallel to the beam axis and thus has an orbital angular
momentum applied thereto. In any fixed radius within the beam, the
Poynting vector follows a spiral trajectory around the axis. Rows
are labeled by l, the orbital angular momentum quantum number, L=l
is the beams orbital angular momentum per photon within the output
signal. For each l, the left column 2002 is the light beam's
instantaneous phase. The center column 2004 comprises the angular
intensity profiles and the right column 2006 illustrates what
occurs when such a beam interferes with a plane wave and produces a
spiral intensity pattern. This is illustrated for orbital angular
momentums of -1, 0, 1, 2 and 3 within the various rows of FIG.
23.
[0166] Referring now to FIG. 21, there is illustrated an
alternative manner in which the OAM generator 1206 may convert a
Hermite-Gaussian beam output from an emitter 1202 to a
Laguerre-Gaussian beams having imparted therein an orbital angular
momentum using mode converters 2104 and a Dove prism 2110. The
Hermite-Gaussian mode plane waves 2102 are provided to a .pi./2
mode convertor 2104. The .pi./2 mode convertor 2104 produce beams
in the Laguerre-Gaussian modes 2106. The Laguerre-Gaussian modes
beams 2106 are applied to either a .pi. mode convertor 2108 or a
dove prism 2110 that reverses the mode to create a reverse
Laguerre-Gaussian mode signal 2112.
[0167] Referring now to FIG. 22, there is illustrated the manner in
which holograms within the OAM generator 1206 generate a twisted
light beam. A hologram 2202 can produce light beam 2204 and light
beam 2206 having helical wave fronts and associated orbital angular
momentum lh per photon. The appropriate hologram 2202 can be
calculated or generated from the interference pattern between the
desired beam form 2204, 2206 and a plane wave 2208. The resulting
holographic pattern within the hologram 2202 resembles a
diffraction grating, but has a l-pronged dislocation at the beam
axis. When the hologram is illuminated with the plane wave 2208,
the first-order diffracted beams 2204 and 2206 have the desired
helical wave fronts to provide the desired first ordered diffracted
beam display 2210.
[0168] Referring now to FIG. 23, there is more particularly
illustrated the manner in which the sample 1210 receives the input
OAM twisted wave 1208 provided from the OAM generator 1206 and
provides an output OAM wave 1212 having a particular OAM signature
associated therewith that depends upon the material or the
concentration of a particular monitored material within the sample
1210. The sample 1210 may comprise any sample that is under study
and may be in a solid form, liquid form or gas form. The sample
material 1210 that may be detected using the system described
herein may comprise a variety of different materials. As stated
previously, the material may comprise liquids such as blood, water,
oil or chemicals. The various types of carbon bondings such as
C--H, C--O, C--P, C--S or C--N may be provided for detection. The
system may also detect various types of bondings between carbon
atoms such as a single bond (methane or Isooctane), dual bond items
(butadiene and benzene) or triple bond carbon items such as
acetylene.
[0169] The sample 1210 may include detectable items such as organic
compounds including carbohydrates, lipids (cylcerol and fatty
acids), nucleic acids (C,H,O,N,P) (RNA and DNA) or various types of
proteins such as polyour of amino NH.sub.2 and carboxyl COOH or
aminos such as tryptophan, tyrosine and phenylalanine. Various
chains within the samples 1210 may also be detected such as
monomers, isomers and polymers. Enzymes such as ATP and ADP within
the samples may be detected. Substances produced or released by
glands of the body may be in the sample and detected. These include
items released by the exocrine glands via tube/ducts, endocrine
glands released directly into blood samples or hormones. Various
types of glands that may have their secretions detected within a
sample 1210 include the hypothalamus, pineal and pituitary glands,
the parathyroid and thyroid and thymus, the adrenal and pancreas
glands of the torso and the hormones released by the ovaries or
testes of a male or female.
[0170] The sample 1210 may also be used for detecting various types
of biochemical markers within the blood and urine of an individual
such as melanocytes and keratinocytes. The sample 1210 may include
various parts of the body to detect defense substances therein. For
example, with respect to the skin, the sample 1210 may be used to
detect carotenoids, vitamins, enzymes, b-carotene and lycopene.
With respect to the eye pigment, the melanin/eumelanin,
dihydroxyindole or carboxylic may be detected. The system may also
detect various types of materials within the body's biosynthetic
pathways within the sample 1210 including hemoglobin, myoglobin,
cytochromes, and porphyrin molecules such as protoporphyrin,
coporphyrin, uroporphyrin and nematoporphyrin. The sample 1210 may
also contain various bacterial to be detected such as propion
bacterium, acnes. Also various types of dental plaque bacteria may
be detected such as porphyromonos gingivitis, prevotella intremedi
and prevotella nigrescens. The sample 1210 may also be used for the
detection of glucose in insulin within a blood sample 1210. The
sample 1210 may also include amyloid-beta detection. Detection of
amyloid-beta within the sample may then be used for determinations
of early onset Alzheimer's. Higher levels of amyloid-beta may
provide an indication of the early stages of Alzheimer's. The
sample 1210 may comprise any material that is desired to be
detected that provides a unique OAM twist to a signal passing
through the sample.
[0171] The orbital angular momentum within the beams provided
within the sample 1210 may be transferred from light to matter
molecules depending upon the rotation of the matter molecules. When
a circularly polarized laser beam with a helical wave front traps a
molecule in an angular ring of light around the beam axis, one can
observe the transfer of both orbital and spin angular momentum. The
trapping is a form of optical tweezing accomplished without
mechanical constraints by the ring's intensity gradient. The
orbital angular momentum transferred to the molecule makes it orbit
around the beam axis as illustrated at 2402 of FIG. 24. The spin
angular momentum sets the molecule spinning on its own axis as
illustrated at 2404.
[0172] The output OAM wave 1212 from the sample 1210 will have an
orbital angular momentum associated therewith that is different
from the orbital angular momentum provided on the input OAM wave
1208. The difference in the output OAM wave 1212 will depend upon
the material contained within the sample 1210 and the concentration
of these materials within the sample 1210. Differing materials of
differing concentration will have unique orbital angular momentums
associated therewith. Thus, by analyzing the particular orbital
angular momentum signature associated with the output OAM wave
1212, determinations may be made as to the materials present within
the sample 1210 and the concentration of these materials within the
sample may also be determined.
[0173] Referring now to FIG. 25, the matching module 1214 receives
the output orbital angular momentum wave 1212 from the sample 1210
that has a particular signature associated therewith based upon the
orbital angular momentum imparted to the waves passing through the
sample 1210. The matching module 1214 amplifies the particular
orbital angular momentum of interest in order to provide an
amplified wave having the desired orbital angular momentum of
interest 1216 amplified. The matching module 1214 may comprise a
matching aperture that amplifies the detection orbital angular
momentum associated with a specific material or characteristic that
is under study. The matching module 1214 may in one embodiment
comprise a holographic filter such as that described with respect
to FIGS. 15A-15D in order to amplify the desired orbital angular
momentum wave of interest. The matching module 1214 is established
based upon a specific material of interest that is trying to be
detected by the system. The matching module 1214 may comprise a
fixed module using holograms as illustrated in FIGS. 15A-15D or a
tunable module in a manner similar to that discussed with respect
to the OAM generation module 1206. In this case, a number of
different orbital angular momentums could be amplified by the
matching module in order to detect differing materials or differing
concentrations of materials within the sample 1210. Other examples
of components for the matching module 1214 include the use of
quantum dots, nanomaterials or metamaterials in order to amplify
any desired orbital angular momentum values within a received wave
form from the sample 1210.
[0174] Referring now to FIG. 26, the matching module 1214 rather
than using holographic images in order to amplify the desired
orbital angular momentum signals may use non-linear crystals in
order to generate higher orbital angular momentum light beams.
Using a non-linear crystal 2602, a first harmonic orbital angular
momentum beam 2604 may be applied to a non-linear crystal 2602. The
non-linear crystal 2602 will create a second order harmonic signal
2606.
[0175] Referring now to FIG. 27, there is more particularly
illustrated the detector 1218 to which the amplified orbital
angular momentum wave 1216 from the matching circuit 1214 in order
that the detector 1218 may extract desired OAM measurements 2602.
The detector 1218 receives the amplified OAM waves 1216 and detects
and measures observable changes within the orbital angular momentum
of the emitted waves due to the presence of a particular material
and the concentration of a particular material under study within
the sample 1210. The detector 1218 is able to measure observable
changes within the emitted amplified OAM wave 1216 from the state
of the input OAM wave 1208 applied to the sample 1210. The
extracted OAM measurements 2702 are applied to the user interface
1220. The detector 618 includes an orbital angular momentum
detector 2104 for determining a profile of orbital angular momentum
states of the orbital angular momentum within the orbital angular
momentum signal 616 and a processor 2106 for determining the
material within the sample responsive to the detected profile of
the orbital angular momentum states of the orbital angular
momentum. The manner in which the detector 1218 may detect
differences within the orbital angular momentum is more
particularly illustrates with respect to FIG. 28-30.
[0176] FIG. 28 illustrates the difference in impact between spin
angular polarization and orbital angular polarization due to
passing of a beam of light through a sample 2802. In sample 2802a,
there is illustrated the manner in which spin angular polarization
is altered responsive to a beam passing through the sample 2802a.
The polarization of a wave having a particular spin angular
momentum 2804 passing through the sample 2802a will rotate from a
position 2804 to a new position 2806. The rotation occurs within
the same plane of polarization. In a similar manner, as illustrated
with respect to sample 2802b, an image appears as illustrated
generally at 2808 before it passes through the sample 2802b. Upon
passing the image through the sample 2802b the image will rotate
from the position illustrated at 2810 to a rotated position
illustrated at 2812. The amount of rotation is dependent upon the
presence of the material being detected and the level of
concentration of the material being detected within the sample
2802. Thus, as can be seen with respect to the sample 2802 of FIG.
28, both the spin angular polarization and the orbital angular
momentum will change based upon the presence and concentration of
materials within the sample 2802. By measuring the amount of
rotation of the image caused by the change in orbital angular
momentum, the presence and concentration of a particular material
may be determined.
[0177] This overall process can be more particularly illustrated in
FIG. 29. A light source 2902 shines a light beam through expanding
optics 2904. The expanded light beam is applied through a metalab
generated hologram 2906 that imparts an orbital angular momentum to
the beam. The twisted beam from the hologram 2906 is shined through
a sample 2908 having a particular length L. As mentioned
previously, the sample 2908 may be located in a container or in its
naturally occurring state. This causes the generation of a twisted
beam on the output side of the sample 2908 to create a number of
detectable waves having various orbital angular momentums 2910
associated therewith. The image 2912 associated with the light beam
that is applied to sample 2908 will rotate an angle .phi. depending
upon the presence and concentration of the material within the
sample 2908. The rotation .phi. of the image 2912 is different for
each value orbital angular momentum -l or +l. The change in
rotation of the image .DELTA..phi. may be described according to
the equation:
.DELTA..phi.=.phi..sub.1-.phi..sub.-1=f(l, L, C)
Where l is orbital angular momentum number, L is the path length of
the sample and C is the concentration of the material being
detected.
[0178] Thus, since the length of the sample L is known and the
orbital angular momentum may be determined using the process
described herein, these two pieces of information may be able to
calculate a concentration of the material within the provided
sample.
[0179] The above equation may be utilized within the user interface
more particularly illustrated in FIG. 30. The user interface 1220
processes the OAM measurements 3002 using an internal algorithm
3002 that provides for the generation of material and/or
concentration information 3004 that may be displayed in some type
of user display. The algorithm would in one embodiment utilize that
equation described herein above in order to determine the material
and/or concentration based upon the length of a sample and the
detected variation in orbital angular momentum. The process for
calculating the material and/or concentration may be done in a
laboratory setting where the information is transmitted wirelessly
to the lab or the user interface can be associated with a wearable
device connected to a meter or cell phone running an application on
the cell phone connected via a local area network or wide area
network to a personal or public cloud. The user interface 3020 of
the device can either have a wired or wireless connection utilizing
Bluetooth, ZigBee or other wireless protocols.
[0180] Referring now to FIG. 31, there is illustrated the manner in
which the various data accumulated within the user interface 1220
that has been collected in the manner described herein above may be
stored and utilized for higher level analysis. Various devices 3102
for collecting data as described herein above may communicate via
private network clouds 3104 or with a public cloud 3106. When
communicating with a private cloud 3104, the devices 3102 merely
store information that is associated with a particular user device
that is for use with respect to analysis of the user associated
with that user device. Thus, an individual user could be monitoring
and storing information with respect to their present glucose
concentrations in order to monitor and maintain their diabetes.
[0181] Alternatively, when information is compiled from multiple
devices 3102 within the public cloud 3106, this information may be
provided directly to the public cloud 3106 from the individual
devices 3102 or through the private clouds 3104 of the associated
network devices 3102. Utilizing this information within the public
cloud 3106 large databases may be established within servers 3108
associated with the public cloud 3106 to enable large scale
analysis of various health related issues associated with the
information processed from each of the individual devices 3102.
This information may be used for analyzing public health
issues.
[0182] Thus, the user interface 1220 in addition to including the
algorithm 3002 for determining material and/or concentration
information 3004 will include a wireless interface 3006 enabling
the collected information to be wirelessly transmitted over the
public or private cloud as described with respect to FIG. 31.
Alternatively, the user interface may comprise a storage database
3008 enabling the collected information to be locally stored rather
than transmitted wirelessly to a remote location.
[0183] Referring now to FIG. 32, there is illustrated a particular
example of a block diagram of a particular apparatus for measuring
the presence an concentration of glucose using the orbital angular
momentum of photons of a light beam shined through a glucose
sample. While the present example is with respect to the detection
of glucose, one skilled in the art would realize that the example
would be applicable to the detection of the presence and
concentration of any material. The process creates a second-order
harmonic with helical light beam using a non-linear crystal such as
that described with respect to FIG. 25. The emission module 2402
generates plane electromagnetic waves that are provided to an OAM
generation module 3204. The OAM generation module 3204 generates
light waves having an orbital angular momentum applied thereto
using holograms to create a wave having an electromagnetic vortex.
The OAM twisted waves are applied to the sample 3206 that is under
study in order to detect the glucose and glucose concentration
within a sample. A rotated signature exits the sample 3206 in the
manner described previously with respect to FIGS. 28-29 and is
provided to the matching module 3208. The matching module 3208 will
amplify the orbital angular momentum such that the observed
concentrations may be calculated from the orbital momentum of the
signature of the glucose. These amplified signals are provided to
detection module 3210 which measures the radius of the beam w(z) or
the rotation of the image provided to the sample via the light
beam. This detected information is provided to the user interface
that includes a sensor interface wired or wireless Bluetooth or
ZigBee connection to enable the provision of the material to a
reading meter or a user phone for the display of concentration
information with respect to the sample. In this manner
concentrations of various types of material as describe herein may
be determined utilizing the orbital angular momentum signatures of
the samples under study and the detection of these materials or
their concentrations within the sample determine as described.
[0184] Provided the orthogonality of Laguerre polynomials, Laguerre
Gaussian beams exhibiting orbital angular momentum (OAM) have been
determined as a basis for spatial division multiplexing (SDM) in
communication applications using for example a mux-demux optical
element design. OAM beams are also of interest in quantum
informatics. OAM also enables the probing of solutions of chiral
and non-chiral molecules.
[0185] FIG. 33 illustrates a further optical configuration for
transmitting and detecting information. The twisted nematic LCOS
SLM 3302 implements a 1024.times.768 array with 9 .mu.m pitch and
8-bit resolution covering the visible wavelength range (430-650 nm)
and readily interfaced via a VGA connection. A programmable SLM
3302 allows for the generation of a variety of engineered beams. A
twisted nematic (TN) liquid crystal on silicon (LCOS) SLM is
particularly useful in realizing the holograms that modulate the
phase front of the input plane wave 102 (FIG. 1) or Gaussian beam.
An SLM is computer addressable using common software packages such
as Matlab or Mathematica to define an arbitrary two-dimensional
phase shift imprinted onto the beam input using, for example, a
hologram.
[0186] A collimated input beam is reflected off of a display
appropriately encoded by a phase retarding forked gratings, or
hologram. The generating equation for the forked gratings may be
written as a Fourier series:
T ( r , .PHI. ) = m = - .infin. .infin. t m exp [ - m ( 2 .pi. D r
cos .PHI. - l .PHI. ) ] ##EQU00015##
[0187] Where r and .phi. are the coordinates, l is the order of the
vorticity and D is the period of the rectilinear grating far from
the forked pole. The weights, t.sub.m, of the Fourier components of
the phase grating may be written in terms of Bessel functions of
integer order:
t.sub.m=(-i).sup.mJ.sub.m(k.beta.)exp(ik.alpha.).
[0188] Where k.alpha. and k.beta. bias and modulate the phase of
the forked grating, respectively. Typically only a handful of terms
of this series are needed to generate the OAM beams. For example,
success has been had with the transfer pattern:
T ( r , .PHI. ) = 1 2 - 1 2 sin ( 2 .pi. D r cos .PHI. - l .PHI. )
##EQU00016##
[0189] Referring now back to FIG. 33, there is illustrated the
optical configuration for detecting a unique signature of a signal
passing through a sample under test 3303. The sample 3303 may be in
a container or in its naturally occurring state. At a high-level,
the instrument comprises a Mach Zehnder interferometer. One arm of
the interferometer propagates a reference beam 3310. The reference
beam 3310 is created by a laser 3304 generating a light beam
including a plurality of plane waves that is transmitted through a
telescope 3306. The plane wave light beam from the telescope 3306
passes through a first beam splitter 3308. The beam splitter 3308
generates the reference beam 3310 that is reflected from a mirror
3311 to an interfering circuit 3312. The reference beam 3310 may be
a plane wave or, with the addition of a lens, a spherical wavefront
may be implemented. This arm is blocked for amplitude only
measurements.
[0190] In a second arm, the split plane wave beam from the beam
splitter 3308 is combined at a beam combiner 3314 with the beam
provided from the spatial light modulator 3302. The spatial light
modulator 3302 provides a light beam including the forked hologram
3316. The beam combiner 3314 combines the forked hologram beam 3318
from the SLM 3302 and a plane wave beam 3320 from the laser 3304 to
generate an OAM or other orthogonal function twisted beam of a
known signature. This beam is reflected through a series of mirrors
3322 and focused on a pinhole aperture 3324 before passing the beam
having the known orbital angular momentum through the sample under
test 3303.
[0191] The sample twisted beam 3326 has been interfered at the
signal combiner 3312 with the reference beam 3310. This interfered
image may then be recorded by a camera or recording device 3328.
This provides a unique OAM signature 3330 that may be analyzed in
order to detect materials within the sample under test 3303. As can
be seen, the unique OAM signature 3330 is different from the
signature 3332 of the transmitted beam. The manner in which the
signature is altered will be more fully described herein below.
[0192] In the second arm, the LCOS SLM 3302 is used to transform a
collimated plane wave input beam 3320 into an OAM encoded beam. The
SLM 3302 is driven by a Matlab programs on an extended laptop
display to provide a display of a forked hologram of any l or
.rho.. Following the SLM 3302, the beam is reflected through three
mirrors 3322 to provide a sufficient distance for the separation of
the diffracted OAM modes such that a pinhole iris aperture 3324 may
select the desired mode to pass through a sample under test
3303.
[0193] Several materials of interest may be detected with OAM
signatures using the setup of FIG. 33. Examples of these materials
include acetone, isopropyl alcohol, sucrose, amyloid-beta, and
glucose in steam distilled water. Spectroscopic grade soda lime
glass cuvettes (1 cm.times.2.5 cm.times.3 cm) or larger custom-made
circular cuvettes having BK7 cover glass in caps may be utilized
for containing the sample under test 3303.
[0194] The sample under test 3303 is mounted on a translation stage
arranged to allow quick and repeatable positioning in and out of
the beam path either by movement of the sample or movement of the
beam projection apparatus. Additionally, back reflections from the
sample services are monitored carefully and blocked by irises so no
spurious, secondary interactions occur. The optical power through
samples is low (less than 25 .mu.W) to avoid any refractive index
dependent thermal gradients in the solution.
[0195] The insertion of wave plates, variable retarders and
polarizers before and after the sample under test has not revealed
any remarkable results. While glucose is well-known to have a
polarimetric response at these wavelengths, the concentration path
length product is too small to produce a notable shift in the state
of polarization. This suggests that the OAM and glucose is a more
pronounced response then polarimetry of the molecule.
[0196] Images 3330 of the beam at the output of the instrument are
recorded using the high-resolution DSLR camera 3328 that is
securely mounted perpendicular to the beam propagation direction
and remotely triggered to prevent vibration or shift in the
instrument. Measurement of ellipticity is performed using Photoshop
and Matlab or similar types of image measuring and processing
software or applications.
[0197] With this instrument, the change to an OAM state imparted on
the input beam by a sample under test 3303 can be quantified in
both intensity and phase. A series of experiments has been
performed using primarily aqueous glucose solutions. A 15% stock
solution was diluted to a variety of desired concentrations.
Because the different isomers of the sugar interact with each other
before attaining equilibrium, a settling time is required for a new
or altered solution. Solutions were allowed to equilibrate
overnight (approximately 15 hours), a time much longer than the
recommended 2 hours, in a Cuvette that was capped to prevent
evaporation.
[0198] As mentioned previously with respect to FIG. 1, passing
through the sample 3303 causes a unique OAM signature to be
imparted to the light beam passing through the sample. This unique
OAM signature provides an identification of the presence of a
material within the sample and of the concentration of the material
within the sample. This unique OAM signature includes a number of
differences from the OAM signal signature that is input to the
sample 3303. The unique OAM signature characteristics are
illustrated in FIGS. 34-36. FIG. 34 illustrates the manner in which
the ellipticity of the OAM intensity diagram changes after passing
through the sample 3303. Initially, as illustrated at 3402, the
intensity diagram has a substantially circular shape from the plane
wave OAM beam before passing through the sample 3303. After passing
through the sample 3303, the intensity diagram has a much more
elliptical shape as illustrated generally at 3404. This elliptical
shape is a unique characteristic that is different depending upon a
material being detected and the concentration of the substance
being detected. By detecting the ellipticity of the intensity
diagram, a determination may be made of the presence of a
particular material within the sample.
[0199] FIG. 35 illustrates a further characteristic of the OAM
signature that may be altered by passing through a sample 3303. In
this case, the center of gravity of the intensity diagram has been
shifted. Position 3502 illustrates the initial position of the
center of gravity of the intensity diagram before passing through a
sample 3303. After passing through the sample 3303, the center of
gravity moves to location 3504 that is a noticeable shift from the
original position prior to passing through the sample. The shift is
uniquely affected by different materials. Thus, the shift in center
of gravity may also be used as an OAM distinct signature
characteristic with the center of gravity shift indicating the
presence of a particular material and the concentration of the
material. Based upon an analysis of the shift in the center of
gravity of the intensity diagram, a determination of the presence
and/or concentration of a material may be made.
[0200] A final distinct OAM signature characteristic is illustrated
in FIG. 36. In this case, the major axis 3602 of the intensity
diagram ellipse shifts from a first position 3602 to a second
position 3604 over an angle .theta. 3606. The major axis of the
intensity diagram ellipse rotates from a position 3602 to position
3604 based upon the material being detected. The angle .theta. is
uniquely associated with a particular substance and concentration
of the substance being detected. Thus, a material may be detected
based upon a determined angle .theta. within the intensity
diagram.
[0201] A mathematical model may be used to represent the unique OAM
signatures provided by each of changes in eccentricity, shift or
translation of the center of gravity in rotation of the axis. The
change in eccentricity may be represented by:
circle x 2 + y 2 + z 2 [ x y z ] [ x y z ] ##EQU00017## 3 -
dimensional ellipse [ x y z ] [ 1 / a 2 0 0 0 1 / b 2 0 0 0 1 / c 2
] [ x y z ] ##EQU00017.2##
Where a, b, c are dimensions of the ellipse.
[0202] The change in the center of gravity may be represented by a
shift or translation in space of a vector v according to the
matrix:
translation [ 1 0 v x 0 1 v y 0 0 v z ] ##EQU00018##
[0203] The rotations of the axis may be represented by a series of
matrices showing rotations in 3-different orientations:
[ 1 0 0 0 cos .alpha. - sin .alpha. 0 sin .alpha. cos .alpha. ] [
cos .beta. 0 sin .beta. 0 1 0 - sin .beta. 0 cos .beta. ] [ cos
.gamma. - sin .gamma. 0 sin .gamma. cos .gamma. 0 0 0 1 ]
##EQU00019##
[0204] Rotation by .alpha. Rotation by .beta. Rotation by
.gamma.
[0205] In an example illustrated in FIGS. 37A and 37B there is
shown the application of an OAM beam to a sample consisting only of
water (FIG. 37A) and of water including a 15% glucose concentration
(FIG. 37B). An l=7 OAM beam at 543 nm is propagated through a 3 cm
Cuvette of only water to provide the intensity diagram illustrated
in FIG. 37A. The intensity diagram illustrated in FIG. 37B is
provided when the l=7 OAM beam passes through a 15% glucose
solution in water. The OAM signature manifests itself as an induced
ellipticity on the ordinary circular beam amplitude illustrated in
the intensity diagram of FIG. 37A. The distinct signature effect
may also be observed in phase diagrams such as that illustrated in
FIGS. 38A and 38B. FIGS. 38A and 38B illustrate interferograms of
an l=2 OAM beam at 633 nm propagating through a 3 cm cuvette of
water (FIG. 38A) and a 3 cm cuvette of 15% glucose in water (FIG.
38B). In this particular interferance, the reference beams have the
same spherical wave fronts. This is why essentially spiral pattern
is observed in the phase measurements. Note in particular, the
torsional shift in one of the 2 spirals of the phase front of the
sample propagating through the glucose solution. The shift in the
spiral pattern is the signature of the interaction in this
experiment.
[0206] An unperturbed OAM mode propagates through several meters of
free space. Glucose samples appear to impart a phase perturbation
on an OAM beam causing the OAM mode to topologically be involved in
the propagation direction. This effect allows for more sensitive
metrology. FIG. 39 shows the amplitude of an OAM beam and FIG. 40
shows the phase of an OAM beam. The beam is an OAM l=beam and is
perturbed when passing through a 3 cm Cuvette of a 5% glucose
solution and a plane four meters beyond the Cuvette. The
ellipticity of the beam is much more pronounced in both amplitude
and phase measurements.
[0207] The OAM signature is nonlinear with respect to glucose
concentrations and under some conditions, appears to be somewhat
periodic with concentration. The ellipticity as a function of
glucose concentration is plotted in FIG. 41 using a 3 cm Cuvette,
OAM modes l=5, 6, 7, for concentrations of glucose between 5% and
9% in water. Though the preliminary data is noisy, the trend
persists over several OAM modes.
[0208] There is a broad absorption band for glucose centered at
approximately 750 nm, with a FWHM (Full Width Half Maximum), as
understood by a person of skill in the art, of approximately 250
nm. Given that the 543 nm absorbance of glucose is 4 times smaller
than that for 633 nm, it is interesting that the formal wavelength
provides a stronger OAM response. This suggests the interaction is
based on the real part of the susceptibility, .chi.', rather than
its imaginary part, .chi.''. We note as well that in a separate
polarimetry characterization of glucose, using sample cells as long
as 20 cm, we measured a 50% larger specific rotation at 543 nm than
at 633 nm. In the OAM work, however, we found no discernable change
in the effect with polarization, nor did we observe a change in the
state of polarization of the beam through the 3 cm samples. This is
in keeping with the previous polarization studies of OAM with
chiral molecules.
[0209] As a check for whether the vorticity of the OAM beam was
important for the effect, and annulus was used to project a simple
ring of light through a glucose sample. The annulus pattern was
printed on a traditional plastic transparency sheet and illuminated
with a magnified and collimated 543 nm laser beam. As can be seen
in FIGS. 42A-42C, no distortion or signature was observed through
Cuvette's of water (FIG. 42B) or Glucose (FIG. 42C) solution.
Varying the ring diameter did not change these no results, even for
diameters larger than the typical OAM beam. When the annulus
diameter was larger than the Cuvette, obvious clipping was
observed. The power level of the beams in this test was as much in
order of magnitude higher than in the OAM experiments. Thus, any
thermal effects would have been accentuated.
[0210] Since aqueous solutions of glucose were used in the
experiments, the study of propagation of OAM in water is relevant.
Steam distilled water, the solvent used in dilution, was placed in
clean new cells of the variety of links and cross-sections and
propagation of a variety of OAM beams through this medium was
measured. No discernible differences were observed among an OAM
mode propagated through a dry cell, a sample of path length 0.5 cm
and a sample of 8 cm of water.
[0211] Another null result was observed in an experiment were in an
OAM beam was propagated through a liquid crystal that variable
retarder. In FIG. 43, reference Nos. 4302, 4304 and 4306 show an
l=7 OAM mode at the output of a variable wave plate for differing
drive voltages between 0.1 V and 6 V.
[0212] It is been noted that the eccentricities of the intensity
images produced by shining orthogonal function processed beam
through a sample can have variances due to a number of differing
factors. FIG. 44 illustrates an example wherein a light beam
produced by a laser 4402 is altered by a hologram provided by an
SLM 4404 to generate an OAM twisted beam 4406. The OAM twisted beam
in addition to being altered by OAM functions may also be processed
using Hermite Gaussian functions, Laguerre Gaussian functions or
any other type of orthogonal function. The OAM twisted beam is
focused through a system 4408 of lenses and mirrors to direct the
beam through a mode sorter 4410. The beam is separated into its
different modes when regenerated at mode sorter 4412 and the
intensity images may be registered by a camera 4414.
[0213] The beam from the laser 4402 has an inherent eccentricity of
approximately 0.15. As illustrated in FIG. 45, there are
illustrated various OAM modes produced by the SLM in column 4502
for l=5,4,3,2,1. As can be seen, there are differences between the
eccentricity of the modes produced by the SLM, and the eccentricity
of the modes regenerated by the second mode sorter 4412.
[0214] Measurements of eccentricity are performed using Photoshop
and Matlab to identify the specific signatures. Referring now to
FIG. 46, there is illustrated an example of an ellipse 4602 having
a radius "a" along its long axis, a radius "b" along a short axis
and a distance "c" to the foci 4604 of the ellipse. The
eccentricity of the ellipse is represented by the equation
eccentricity=c/a. The eccentricity varies from 0 to 1 with 0
representing a circle and 1 representing a line. The eccentricity
equation is calculated according to the following equations:
U xx = 1 N i = 1 N x i 2 + 1 12 ##EQU00020## U yy = 1 N i = 1 N y i
2 + 1 12 ##EQU00020.2## U xy = 1 N i = 1 N y i x i ##EQU00020.3##
common = ( U xx - U yy ) 2 + 4 U xy 2 ##EQU00020.4## 2 a = 2 2 U xx
U yy + common ##EQU00020.5## 2 b = 2 2 U xx U yy - common
##EQU00020.6## c = a 2 - b 2 ##EQU00020.7## Eccentricity = c a
##EQU00020.8##
where x.sub.i is the x location of the pixels in the ellipse;
y.sub.i is the y locations of the pixels in the ellipse; and N is
the number of pixels in the ellipse.
[0215] It is been found that the eccentricity is greater than 0
when no sample is present within the cuvette. A number of factors
contribute to the nonzero eccentricity. OAM twisted signals have
been found to provide different eccentricities based upon a number
of different factors that may affect the index of refraction. These
factors include things such as the sample distribution of the
material within the cuvette due to gravity, the distance of the
camera from the spatial light modulator and the camera angle of the
camera from the spatial light modulator. Other factors affecting
the eccentricity are the cuvette positioning, the index of
refraction changes do to the sample, the cuvette shape and the beam
incidence and exit angle from the cuvette.
[0216] Several image processing factors have also been determined
not to cause changes that are outside the margin of error. Changes
based on software processing errors, a circular mask that is not
OAM, the sample sitting time or the sample interaction with the
glass or plastic comprising the sample container may provide
eccentricity changes, but the changes are not due to optical
impairments caused by the cuvette orientation, camera alignment,
etc. These factors do produce some changes in eccentricity, but
they are within the margin of error and the majority of the
eccentricity change is based on the signature of the molecule being
detected.
[0217] Referring now to FIG. 47, there is illustrated a flow
diagram for analyzing intensity images taken by the camera 4414.
The intensity image has applied thereto threshold double precision
amplitude to enable the ring to be clearly seen without extra
pixels outside of the ring at step 4702. Next at step 4701, both
columns and rows are scanned along for the entire image. The peaks
of the two largest hills and their locations are determined at step
4706. An ellipse is fit at step 4008 for all peak locations found.
Finally, at step 4710, a determination is made of the major and
minor axis of the ellipse, the focal point of the ellipse, the
centroid, eccentricity and orientation of the ellipse.
[0218] FIG. 48 illustrates an ellipse fitting algorithm flowchart.
The X and Y pixel locations are input at step 4802 for all peaks
that are found. An initial guess is provided at step 4804 for the
conic equation parameters. The conic equation parameters comprise
parameters A, B, C, D and E for the equation
Ax.sup.2+By.sup.2+Cx+Dy+E=0. The conjugate gradient algorithm is
used at step 4806 to find conic equation parameters that provide an
optimal fit. An orientation of the ellipse is determined at step
4808 and moved to determine the major and minor axis. The
determination of step 4808 is determined according to the
equation
.0. = 1 2 tan - 1 B C - A ##EQU00021##
The ellipse orientation is returned at step 4810 to determine the
central point of the ellipse. Finally, at step 4812, a
determination is made if the conic equation represents an ellipse.
For an ellipse parameters A and B will exist and have the same sign
but will not be equal. Based upon this analysis it is been
determined that lateral shift of up to 1 mm can cause significant
changes in the measured eccentricity due to clipping of up to
0.2.
Fractional OAM Signals
[0219] Molecular spectroscopy using OAM twisted beams can leverage
fractional OAM states as a molecular signature along with other
intensity signatures (i.e. eccentricity, shift of center of mass
and rotation of the elliptical intensity) as well as phase
signatures (i.e. changes in the phase of the scattered beam) and
specific formation of publicity distributed spectrum. The method of
optical orientation of electronics been by circularly polarized
photons has been heavily used to study spin angular momentum in
solid state materials. The process relies on spin-orbit coupling to
transfer angular momentum from the spin of protons to the spin of
electrons and has been Incorporated into pump-probe Kerr and
Faraday rotation experiments to study the dynamics of optically
excited spends. By enabling the study is spin decoherence,
transport and interactions, this strategy has played a role in the
development of semiconductor spintronics.
[0220] The proposed spectroscopy technique focuses instead on
localized orbital angular momentum (OAM) and solids. Specifically,
one can distinguish between delocalized OAM associated with the
envelope wave function which may be macroscopic in spatial extent,
and local OAM associated with atomic sites, which typically is
incorporated into the effect of spin and associated electronic
states. The former type of angular momentum is a fundamental
interest to orbital fleet coherent systems, for example, quantum
Hall layers, superconductors and topological insulators. Techniques
to study non-equilibrium delocalized OAM in these and other systems
create opportunities to improve understanding of scattering and
quantum coherence of chiral electronic states, with potential
implications for materials discovery.
[0221] The interaction of light with glucose in beta amyloid and
the spectroscopy applications of OAM with respect to these.
Additionally the transfer of OAM between acoustic and photonic
modes in an elliptical fiber, the generation of Rahman sideband
carrying OAM, OAM using a pleasant Monica lens, the study of
optically coherent OAM in excite ons using for wave mixing in the
application of linearly polarized light to create a 2-D pleasant
Monica analog to OAM light in patterned sin metallic film, and the
possibility of OAM light producing spin polarized vote till
electronics for efficient semiconductors may also find application
in these techniques.
[0222] Referring now to FIG. 49, one manner for using nested
fractional OAM states to alleviate the problems associated with
integer OAM states and to enable the use of stable states of
fractional OAM for similar purposes as those described herein
above. In this case the input signals 4902 are provided to
fractional OAM generation circuitry 4904. The fractional OAM
generation circuitry 4904 generates output signals 4906 having
fractional orthogonal states which may then be further applied or
detected as discussed herein.
[0223] The orbital angular momentum of light beams is a consequence
of their azimuthal phase structure. Light beams have a phase factor
exp(im.phi.), where m is an integer and .phi. is the azimuthal
angle, and carry orbital angular momentum (OAM) of m per photon
along the beam axis. These light beams can be generated in the
laboratory by optical devices, such as spiral phase plates or
holograms, which manipulate the phase of the beam. In cases where
such a device generates an light beam with an integer value of m,
the resulting phase structure has the form of |m| intertwined
helices of equal phase. For integer values of m, the chosen height
of the phase step generated by the optical device is equal to the
mean value of the OAM in the resulting beam.
[0224] Recently, spiral phase steps with fractional step height as
well as spatial holograms have been used to generate light beams
with fractional OAM states. In these implementations, the
generating optical device imposes a phase change of exp(iM.phi.)
where M is not restricted to integer values. The phase structure of
such beams shows a far more complex pattern. A series of optical
vortices with alternating charge is created in a dark line across
the direction of the phase discontinuity imprinted by the optical
device. In order to obtain the mean value of the orbital angular
momentum of these beams, one has to average over the vortex
pattern. This mean value coincides with the phase step only for the
integer and half integer values. There are certainly more
connections between optics and quantum theory to represent beams
with fractional OAM as quantum states.
[0225] The theoretical description of light modes with fractional
OAM is based on the generating optical device. For integer OAM
values, a theoretical description may exist which provides the way
to treat the angle itself as quantum mechanical Hermitian operator.
The description can provide the underlying theory for a secure
quantum communication system and give form to the uncertainty
relation for angle and angular momentum. The theory may be
generalized for fractional values of M thereby creating a quantum
mechanical description of fractional OAM. Such a rigorous
formulation is of particular interest is the use of half integer
spiral phase plates have been used to study high dimensional
entanglement. Fractional OAM states are characterized not only by
the height of the phase step, but also by the orientation of the
phase dislocation .alpha.. For half odd integer values of M, M mod
1=1/2, states with the same M but a .pi. difference in .alpha. are
orthogonal. In light of recent applications of integer OAM in
quantum key distribution in the conversion of spin to orbital
angular momentum in an optical medium, a rigorous formulation is
important for possible applications of fractional OAM to quantum
communication.
[0226] The component of the OAM in the propagation direction Lz and
the azimuthal rotation angle form a pair of conjugate variables
(just like time-frequency or space-momentum). Unlike linear
position and momentum, which are both defined on an unbound and
continuous state space, the state spaces for OAM and the rotation
angle are different in nature. The OAM eigenstates form a discrete
set of states with m taking on all integer values. Eigenstates of
the angle operator are restricted to a 2.pi. radian interval since
it is physically impossible to distinguish between rotation angles
differing by less than 2.pi. radians. The properties of the angle
operator are rigorously derived in an arbitrarily large, yet finite
state space of 2 L+1 dimensions. This space is spanned by the
angular momentum states |m with m ranging from -L, -L+1, . . . , L.
Accordingly, the 2.pi. radian interval [.theta.0, .theta.0+2.pi.)
is spanned by 2 L+1 orthogonal angle states|.theta.n with
.theta.n=.theta.0+2.pi.n/(2 L+1). Here, .theta..sub.0 determines
the starting point of the interval and with it a particular angle
operator .phi. .theta.. Only after physical results have been
calculated within this state space is L allowed to tend to
infinity, which recovers the result of an infinite but countable
number of basis states for the OAM and a dense set of angle states
within a 2.pi. radian interval.
[0227] A quantum state with fractional OAM is denoted by |M, where
M-m+.mu. and m is the integer part and .mu. .di-elect cons. [0, 1)
is the fractional part. The state |M is decomposed in angle states
according to:
M = ( 2 L + 1 ) - 1 2 n = 0 2 L exp ( M .theta. n ) .theta. n M = (
2 L + 1 ) - 1 2 n = 0 2 L exp ( m .theta. n ) exp ( .mu. .theta. n
) .theta. n ##EQU00022##
It is important to note that .alpha. is bounded by
0.ltoreq..alpha.<2.pi., so that the orientation of the
discontinuity is always understood as measured from 0.sub.0. With
this construction the fractional state |M can be written as:
M ( .alpha. ) = ( 2 L + 1 ) - 1 2 exp ( i .mu. .alpha. ) n = 0 2 L
exp ( M .theta. n ) exp [ 2 .pi. .mu. f .alpha. ( .theta. n ) ]
.theta. n ##EQU00023##
[0228] In integer based OAM generation applications light beams may
be generated using a spiral phase plate. However, light beams
generated using a spiral phase plate with a non-integer phase step
are unstable on propagation. However, one can generate light
carrying fractional orbital angular momentum beams not with a phase
step of a spiral phase plate but by a synthesis of
Laguerre-Gaussian modes. This may be accomplished as illustrated in
FIG. 50 using a spatial light modulator 5002. Input signals 5004
are provided to the spatial light modulator 5002 and used for the
generation of fractional OAM beams 5006. The spatial light
modulator 5002 synthesizes Laguerre Gaussian modes rather than
using a phase step of a spiral phase plate. By limiting the number
of Gouy phases in the superposition, one can produce a light beam
from the SLM 5002 which is well characterized in terms of its
propagation. The structural stability of these fractional OAM light
beams from an SLM make them ideal for communications using
fractional OAM states. Additionally as will be described herein
below the beams would be useful for concentration measurements of
various organic materials.
[0229] Using the spatial light modulator 5002, a light beam with
fractional OAM may be produced as a generic superposition of light
modes with different values of m. As illustrated in FIG. 51,
various Laguerre-Gaussian beam modes 5102 may have a superposition
process 5104 applied thereto by the spatial light modulator 5002 in
order to generate the fractional beam outputs 5106. Using the
correspondence between optics and quantum theory, OAM can be
represented as a quantum state. This quantum state 5202 can be
decomposed into a basis of integer OAM states 5204 as generally
illustrated in FIG. 52. The decomposition only determines the OAM
index m which in a superposition of LG beams leaves the index for
the number of concentric rings unspecified. Therefore, one can make
use of this flexibility to find a representation of a fractional
OAM state in terms of superimposed LG beams with a minimal number
of Gouy phases to increase propagation stability. One can produce
these beams using the spatial light modulator 5002 and study their
propagation and vortex structure. Light beams constructed in this
manner are in excellent realization of non-integer OAM states and
are more stable on propagation and light emerging from fractional
faced steps of a spiral phase plate.
[0230] Referring now to FIG. 53, there is illustrated the manner in
which an SLM may be programmed to provide fractional OAM beams.
Rather than using multiple optical elements to generate each
Laguerre Gaussian mode separately a single SLM 5302 may be
programmed with a hologram 5304 that sets the phase structure 5306
and intensity structure 5308 for generating the superposition. A
blazed grating 5310 is also included in the hologram 5304 to
separate angularly the first fractional order. The formula for the
resulting phase distribution of the hologram 5304 and rectilinear
coordinates .PHI.(x,y).sub.holo is given by:
.PHI.(x, y).sub.holo=[.PHI.(x,y).sub.beam+.PHI.(x,
.LAMBDA.).sub.grating mod
2.pi.-.pi.]sinc.sup.2[(1-I(x,y).sub.beam).pi.]+.pi.
[0231] In this equation .PHI.(x, y) beam is the phase profile of
the superposition at the beam waist for z=0 and .PHI.(x, .LAMBDA.)
grating is the phase profile of the blazed grating which depends on
the period of the grating .LAMBDA.. The two phase distributions are
added to modulo 2.pi. and, after subtraction of .pi. are multiplied
by an intensity mask. In regions of low intensity the intensity
mask reduces the effect of the blazed grating 5310, which in turn
leads to reduced intensity in the first diffraction order. The
mapping between the phase depth and the desired intensity is not
linear but rather given by the trigonometric sinc function.
[0232] Referring now to FIG. 54 and FIG. 55, there are illustrated
the steps necessary to generate a hologram for producing a
non-integer OAM beam. Initially, at step 5502 a carrier phase
representing a blazed grating 5402 is added to the phase 5404 of
the superposition modulo 2.pi.. This combined phase 5406 is
multiplied at step 5504 by an intensity mask 5408 which takes
account of the correct mapping between the phase depth and
diffraction intensity 3010. The resulting hologram 5412 at step
5506 is a hologram containing the required phase and intensity
profiles for the desired non-integer OAM beam.
[0233] Referring now to FIG. 56, there are illustrated the
intensity and phase profiles on propagation for a superposition of
10 modes and M=6.5. Intensity and phase profiles 5602, 5604 and
5606 show a sequence of numerical plots for three different
propagation distances of z=0, z=2zR and z=4zR show the changes in
the phase and intensity on propagation from the waist plane into
the far field. The various cross-sections are plotted over a range
of .+-.3w(z) for each value of z. Profiles 5608, 5610 and 5612 show
the corresponding experimental profiles.
[0234] The use of fractional OAM beams may be used in a number of
fashions. In one embodiment, as illustrated in FIG. 57, fractional
OAM beams may be generated from a fractional OAM beam generator
5702. These fractional OAM beams are then shown through a sample
5704 in a manner similar to that discussed herein above. OAM
spectroscopy detection circuitry 5706 may then be used to detect
certain OAM fraction state profiles caused by the OAM beam shining
through the sample 5704. Particular OAM fraction states will have a
particular fractional OAM state characteristics caused by the
sample 5704. This process would work in the same manner as that
described herein above.
[0235] FIG. 58 illustrates one example of a OAM state profile that
may be used to identify a particular material within a sample. In
this case, the highest number of OAM states is illustrated at L=3.
Additional state levels are also illustrated at L=1.5; L=2.75;
L=3.5 and L=4. This particular OAM state profile would be uniquely
associated with a particular material and could be used to identify
the material within a sample when the profile was detected. The
interaction of Laguerre Gaussian light beams with glucose and beta
amyloid have been the initial spectroscopy application of OAM to
sample types.
[0236] The transfer of OAM between the acoustic and photonic modes
in an optical fiber, the generation of Raman side bands carrying
OAM, OAM using a plasmonic lens, the study of optically coherent
OAM in excitons using four-wave mixing, the application of linearly
polarized light to create a 2-D plasmonic analog to OAM light in a
patterned thin metallic film and the possibility of OAM light
producing spin polarized photoelectrons for efficient
semiconductors are other potential spectroscopy applications.
[0237] Other means of generation and detection of OAM state
profiles may also be utilized. For example a pump-probe
magneto-orbital approach may be used. In this embodiment
Laguerre-Gaussian optical pump pulses impart orbital angular
momentum to the electronic states of a material and subsequent
dynamics are studied with femto second time resolution. The
excitation uses vortex modes that distribute angular momentum over
a macroscopic area determined by the spot size, and the optical
probe studies the chiral imbalance of vortex modes reflected off of
a sample. There will be transients that evolve on timescales
distinctly different from population and spin relaxation but with
large lifetimes.
Multi-Parameter Spectroscopy
[0238] A further application of the OAM spectroscopy may be further
refined by identifying items using a number of different types of
spectroscopy to provide a more definitive analysis. Referring now
to FIG. 59, there is generally illustrated a multi-parameter
spectroscopy system 5900. A plurality of different spectroscopy
parameters 5902 may be tracked and analyzed individually. The group
of parameters is then analyzed together using multi-parameter
spectroscopy analysis processor or system 5904 to determine and
identify a sample with output 5906. The different spectroscopic
techniques receive a light beam generated from a light source 5908,
for example a laser, that has passed through a sample 5910 that a
material or concentration of material therein that is being
detected. While the light source of FIG. 59 illustrates a single
laser and light beam, multiple light sources may provide multiple
light beams or a single source may be used to provide multiple
light beams. In one example, development of a single optical
spectroscopy system to fully characterize the physical and
electronic properties of small samples in real time may be
accomplished using the polarization, wavelength, and orbital
angular momentum (OAM) of light. A polarized optical source is used
to characterize the atomic and molecular structure of the sample.
The wavelength of the source characterizes the atomic and molecular
electronic properties of the sample including their degree of
polarizability. OAM properties of the source are principally used
to characterize the molecular chirality, but such new techniques
are not limited to chiral molecules or samples and can be applied
to non-chiral molecules or samples. These three spectroscopy
dimensions combine to greatly improve the process of identifying
the composition of materials. Integrated into a compact handheld
spectrometer, 3D or multi-parameter spectroscopy empowers consumers
with numerous applications including useful real time chemical and
biological information. Combined with other pump-probe spectroscopy
techniques, 3D/multi-parameter spectroscopy promises new
possibilities in ultrafast, highly-selective molecular
spectroscopy. While the following description discusses a number of
different spectroscopy techniques that may be implemented in
multi-parameter spectroscopy system 5900, it should be realized
that other spectroscopy techniques may be combined to provide the
multi-spectroscopy analysis system of the present disclosure.
Optical Spectroscopy
[0239] Spectroscopy is the measurement of the interaction of light
with various materials. The light may either be absorbed or emitted
by the material. By analyzing the amount of light absorbed or
emitted, a materials composition and quantity may be
determined.
[0240] Some of the light's energy is absorbed by the material.
Light of a given wavelength interacting with a material may be
emitted at a different wavelength. This occurs in phenomena like
fluorescence, luminescence, and phosphorescence. The effect of
light on a material depends on the wavelength and intensity of the
light as well as its physical interaction with the molecules and
atoms.
[0241] A schematic of a spectrometer which makes relative
measurements in the optical spectral region of the electromagnetic
spectrum uses light that is spectrally dispersed by a dispersing
element is shown in FIG. 60. In particular, a device 6002, such as
a monochromator, polychromator, or interferometer, selects a
specific wavelength from a light source 6004. This
single-wavelength light interacts with a sample 6006. A detector
6008 is used to measure the spectrum of light resulting from this
interaction. A change in the absorbance or intensity of the
resulting light 6010 is measured as the detector 6008 sweeps across
a range of wavelengths. A range of different spectroscopic
techniques, based on these fundamental measurements, have been
developed such as those discussed in A. Hind, "Agilent 101: An
Introduction to Optical Spectroscopy," 2011.
(http://www.agilent.com/labs/features/2011_101_spectroscopy.html)
which is incorporated herein by reference in its entirety. Here,
attention is given to molecular spectroscopy techniques including
infrared, Raman, terahertz, fluorescence, and orbital angular
momentum spectroscopy.
Molecular Spectroscopy
Infrared Spectroscopy
[0242] Various types of molecular spectroscopy techniques may also
be used in the multi-parameter spectroscopy system. These
techniques include infrared spectroscopy and others.
[0243] Infrared frequencies occur between the visible and microwave
regions of the electromagnetic spectrum as shown in FIG. 61. The
frequency, .nu., measured in Hertz (Hz), and wavelength, .lamda.,
6102 typically measured in centimeters (cm) are inversely related
according to the equations:
v = c .lamda. and .lamda. = c v ##EQU00024##
where c is the speed of light (3.times.10.sup.10 cm/sec).
[0244] The energy of the light is related to .lamda. and .nu.
by
E = hv = hc .lamda. ##EQU00025##
where h is Planck's constant (h=6.6.times.10.sup.-34 J--s).
[0245] The infrared (IR) spectrum 6104 is divided into three
regions: the near-, mid-, and far-IR. The mid IR region includes
wavelengths between 3.times.10.sup.-4 and 3.times.10.sup.-3 cm.
[0246] In the process of infrared spectroscopy, IR radiation is
absorbed by organic molecules. Molecular vibrations occur when the
infrared energy matches the energy of specific molecular vibration
modes. At these frequencies, photons are absorbed by the material
while photons at other frequencies are transmitted through the
material.
[0247] The IR spectrum of different materials typically includes
unique transmittance, T, peaks and absorbance troughs occurring at
different frequencies such as the measured IR spectrum of water
vapor shown in FIG. 62.
[0248] The absorbance, A, is related to the transmittance by
A=log.sub.10(1/T).
Each material exhibits a unique infrared spectral fingerprint, or
signature, determined by its unique molecular vibration modes which
permit identification of the material's composition by IR
spectroscopy. In the case of water vapor (FIG. 62), for example,
the water molecules absorb energy within two narrow infrared
wavelengths bands that appear as absorbance troughs 6202.
Molecular Vibrations
[0249] Referring now to FIG. 63, water molecules exhibit two types
of molecular vibrations: stretching and bending. A molecule 6302
consisting of n atoms 6308 has 3n degrees of freedom. In a
nonlinear molecule like water, three of these degrees are
rotational, three are translational, and the remaining correspond
to fundamental vibrations. In a linear molecule 6302, two degrees
are rotational and three are translational. The net number of
fundamental vibrations for nonlinear and linear molecules is
therefore, 3n-6 and 3n-5, respectively.
[0250] For water vapor, there are two strong absorbance troughs
6202 (FIG. 62) occurring at approximately 2.7 .mu.m and 6.3 .mu.m
as a result of the two stretching vibrational modes 6304 of water
vapor and its bending mode 6306, respectively. In particular, the
symmetric and asymmetric stretching modes 6304 absorb at
frequencies in very close proximity to each other (2.734 .mu.m and
2.662 .mu.m, respectively) and appear as a single, broader
absorbance band in FIG. 62 between the troughs 6202.
[0251] Carbon dioxide, CO.sub.2, exhibits two scissoring and
bending vibrations 6402, 6404 (FIG. 64) that are equivalent and
therefore, have the same degenerate frequency. This degeneracy
appears in the infrared spectrum of FIG. 65 at .lamda.=15 .mu.m.
The symmetrical stretching vibrational mode 6404 of CO.sub.2 is
inactive in the infrared because it doesn't perturb its molecular
dipole moment. However, the asymmetrical stretching vibration mode
6402 of CO.sub.2 does perturb the molecule's dipole moment and
causes an absorbance in CO.sub.2 at 4.3 .mu.m as shown in FIG.
65.
[0252] Both molecular stretching and bending vibration modes of
molecules (FIGS. 63 and 64) can be predicted to useful theoretical
approximation using simple classical mechanics models.
Stretching Vibrations
[0253] The stretching frequency of a molecular bond may be
approximated by Hooke's Law when treated as a simple classical
harmonic oscillator consisting of two equal masses bound by a
spring
v = 1 2 .pi. k m ##EQU00026##
where k is the force constant of the spring and m is the mass of an
atom.
[0254] In the classical harmonic oscillator, the energy depends on
the extent to which the spring is stretched or compressed,
E = 1 2 kx 2 = hv ##EQU00027##
where x is the displacement of the spring. The classical model of
Hooke's Law, however, is inconsistent with the absorbance of energy
by molecules as it would suggest that energy of any frequency is
absorbed. In real molecules, vibrational motion is quantized and
appropriately modeled by the quantum mechanical expression,
E n = ( n + 1 2 ) hv ##EQU00028##
where n is the principal quantum number (n=0,1,2,3 . . . )
characteristic of each permitted energy level.
[0255] The lowest energy level is E.sub.0=1/2h.nu. followed by
E.sub.1=3/2h.nu.. Only transitions to the next energy level are
allowed according to the selection rule. Subsequently, molecules
absorb photonic energy in integer increments of h.nu.. For photon
absorption energies of 2h.nu. or 3h.nu., however, the resulting
absorbance bands are called overtones of the infrared spectrum and
are of lesser intensity than fundamental vibrational bands.
[0256] Atomic bonds within molecules may come apart if stretched
too far and cannot be compressed beyond a certain point. As such,
molecules are actually anharmonic oscillators. The energy of an
anharmonic oscillator as a function of the interatomic distance is
shown in FIG. 66 with an energy minimum occurs at the normal bond
length 6602 (equivalent to a relaxed classical mechanical spring).
As the interatomic distance increases the quantized energy levels
6604 become more closely spaced and the energy reaches a maximum.
The allowed transitions, h.nu. become smaller in magnitude which
gives lower overtone energies than would otherwise be predicted
using the simply harmonic oscillator theory depicted in FIG.
67.
[0257] Though this mathematical framework represents a useful, if
not simple, approximation, the vibrational activity between two
atoms in a large molecule cannot be isolated from the vibrational
behavior of other atoms in the molecule. Vibrations of two bonds
within a molecule may be coupled in such a manner that one
contracts or expands while the other contracts as in either
asymmetrical or symmetrical stretching vibrations. When this occurs
different absorbance frequency bands are observed instead of
superimposed, or degenerate, bands as observed when two identical
atoms in a bond vibrate with an identical force constant.
[0258] Infrared spectroscopy is used to identify material species
by their unique vibrational and rotational optical signatures. A
complementary spectroscopy technique, Raman spectroscopy is used to
identify materials by their unique light-scattering signatures as
discussed in the next section.
Raman Spectroscopy
[0259] Since Raman spectroscopy is a technique used to characterize
a material by the amount of light it scatters. Raman spectroscopy
complements infrared spectroscopy which instead measures the amount
of light absorbed by a material. Raman and infrared spectroscopy
may further be used in conjunctions with OAM and polarization
spectroscopy to further improve analysis results. When light
interacts with matter, changes in the dipole moment of its
molecules yield infrared absorption bands while changes in their
polarizability produce Raman bands. The sequence of observed energy
bands arises from specific molecular vibrations which collectively
produce a unique spectral signature indicative of each type of
molecule. Certain vibrational modes occurring in Raman spectroscopy
are forbidden in infrared spectroscopy while other vibrational
modes may be observed using both techniques or a multi-parameter
technique using OAM. When these latter modes are common to both
techniques, their intensities differ significantly.
[0260] The most frequent interaction of photons with molecules
results in Rayleigh scattering in which photons are elastically
scattered as the result of excited electrons that decay to their
original energy level. Consequently, Rayleigh scattered photons
have the same energy as incident photons.
[0261] With the discovery of inelastic photonic scattering
phenomena in 1928 by C. V. Raman and K. S. Krishnan, Raman
spectroscopy was established as a practical chemical analysis
method useful to characterize a wide variety of chemical species
including solid, liquid, and gaseous samples. Solid crystal lattice
vibrations are typically active in Raman spectroscopy and their
spectra appear in polymeric and semiconductor samples. Gaseous
samples exhibit rotational structures that may be characterized by
vibrational transitions.
[0262] Approximately one percent of incident photons scatter
inelastically, and yield lower energy photons. Raman scattering
results from changes in the vibrational, rotational, or electronic
energy of a molecule. The vibrational energy of the scattering
molecule is equivalent to the difference between incident and Raman
scattered photons. When an incident photon interacts with the
electric dipole of a molecule, this form of vibronic spectroscopy
is often classically viewed as a perturbation of the molecule's
electric field. Quantum mechanically, however, the scattering event
is described as an excitation to a virtual energy state lower in
energy than a real electronic transition with nearly coincident
decay and change in vibrational energy. Such spectroscopy can work
in conjunction with incident photons that carry OAM. In Raman
spectroscopy, incident photons excite electrons to a different
final energy level than its original energy level (FIG. 68).
[0263] Since the intensity of Raman scattering is low, heat
produced by the dissipation of vibrational energy does not yield an
appreciable rise in material temperature. Such Raman spectroscopy
can work in conjunction with incident photons that carry OAM. At
room temperature, the population of vibrationally excited states is
small. Stokes-shifted scattering events shown in FIG. 68 are
typically observed in Raman spectroscopy since at room temperature
the excited vibrational states are low and the electron originates
in the ground state. The inelastic Raman scattered photon 6802 has
lower energy than the incident photon 6804 as the electron decays
to an energy level 6806 higher than the original ground state 6808.
Anti-Stokes shifted scattering events 6810 result from a small
fraction of molecules originally in vibrationally excited states
(FIG. 68) which leave them in the ground state 6812 and results in
Raman scattered photons with higher energy. At room temperature,
anti-Stokes shifted Raman spectra are always weaker than
Stokes-shifted spectrum since the Stokes and anti-Stokes spectra
contain the same frequency information. Most Raman spectroscopy
focuses exclusively on Stokes-shifted scattering phenomena for this
reason.
[0264] The force constant by which the vibrational mode energy may
be modeled is affected by molecular structure including atomic
mass, molecular species, bond order, and the geometric arrangement
of molecules. However, Raman scattering occurs when the
polarizability of molecules may be affected.
[0265] The polarizability, .alpha., of a molecule appears as a
proportionality constant between the electric field and the induced
dipole moment,
P=.alpha.E.
[0266] The induced dipole scatters a photon at the frequency of the
incident photon (Rayleigh scattering). Molecular vibration,
however, may change the polarizability and give rise to inelastic
Raman scattering of photons. Changes in polarizability may be
expressed by
.differential. .alpha. .differential. Q .noteq. 0 ##EQU00029##
where Q is in a direction normal to the vibration, and is
considered a selection rule for Raman-active vibrations.
[0267] Raman-active vibrations are non-existent in the infrared for
molecules having a center of symmetry while the existence of a
perturbed symmetry center (e.g. permanent dipole moment) indicates
the absence of infrared-active vibrations.
[0268] The intensity of a Raman band is proportional to the square
of the spatial change of polarizability, or the induced dipole
moment,
I Raman .varies. ( .differential. .alpha. .differential. Q ) 2 .
##EQU00030##
Hence, incident photons that slightly induce a dipole moment will
yield a Raman band with a very small intensity. Stronger Raman
scattering systems are those with higher values of .alpha. such as
molecules having double carbon bonds which exhibit more broadly
distributed electrons susceptible to polarization. Subsequently,
the range of chemical concentrations measurable by Raman
spectroscopy is considerably wide given that the scattering
intensity is directly proportional to concentration.
[0269] Raman spectroscopy exhibits several advantages over other
spectroscopy techniques. Raman bands exhibit good signal-to-noise
ratios owing to its detection of fundamental vibrational modes.
Hence, the Raman signature of measured samples is typically more
pronounced and definitive.
[0270] Raman spectroscopy is more useful for analyzing aqueous
solutions than infrared spectroscopy since the Raman spectrum of
water is weak and unobtrusive while the infrared spectrum of water
is very strong and more complex. In organic and inorganic
chemistries, the existence of covalent bonds yields a unique Raman
signature. A Raman spectroscopy setup only requires an appropriate
laser source incident on a material and a detector to collect
scattered photons which minimizes the need for elaborate sample
preparation. Raman spectroscopy is non-destructive as the material
is merely illuminated with a laser. Because the Raman effect is
weak, the efficiency and optimization of a Raman spectroscopy
instrument is critically important to providing measurements of the
slightest molecular concentrations within the shortest possible
time.
Spontaneous Raman Spectroscopy
[0271] The intensity of spontaneous Raman scattering is linearly
dependent on the incident intensity of light but of several orders
of magnitude less intense. Treating the light-matter interaction
quantum mechanically, the total Hamiltonian may be expressed in
terms of the energy associated with the vibrational modes of the
molecule, H_.nu., the light, H_.gamma., and their interaction,
H_.nu..gamma.,
H=H_.nu.+H_.gamma.+H_.nu..gamma..
In this framework
H_.nu.=1/2m(p 2+.omega._0 2 q 2)
with vibrational frequency .omega._0 and the normal mode amplitude
q which may be expressed in terms of creation and annihilation
operators of the molecular vibrations,
q= (2.pi./(8.pi. 2 .mu..omega._0))[b .dagger.+b]
with the electric dipole moment .mu.. This leaves
H_.nu.=.omega._0 (b .dagger. b+1/2).
[0272] Using creation and annihilation operators for light, a
.dagger. and a, field quantization is obtained,
E_.lamda.= ((2.pi.h.nu._L)/( V_int)).SIGMA._(k_.lamda.)
e_(k_.lamda.)i[ak_.lamda. .dagger.-ak_.lamda.]
where e_(k_.lamda.) is the field polarization unit vector field and
V_int the interaction volume. The Hamiltonian for the light is
then
H_.gamma.=.SIGMA._(k_.lamda.) .omega._(k_.lamda.)(a_(k_.lamda.)
.dagger. a_(k_.lamda.)+1/2).
Using the first order perturbation of the electric dipole
approximation the interaction Hamiltonian may be obtained in terms
of the molecule's polarizability, .alpha.,
(H_int&=&"E".alpha."E"@&=&"E".alpha._0"E"+(.differential..alpha./.differ-
ential.q)_0"E"q"E"+ . . . )
within the local coordinate system, q. The first term characterizes
Rayleigh scattering. The remaining first order Raman scattering
term is needed to characterize spontaneous Raman scattering
including the coherent laser field, "E" _L, in addition to the
Stokes and anti-Stokes fields, "E"_S and "E"_AS, respectively.
Substituting q and E_.gamma. into this expression yields
.box-solid.(H_int&=&H_.gamma.S+H_.gamma.AS@&.about.&(.differential..alph-
a./.differential.q)_0 .SIGMA._(k_S k_L) ((2.omega._L
.omega._s)/.omega._0)(e_(k_L)"" e_(k_s))(.alpha._(k_S) .dagger. b
.dagger. .alpha._(k_L)"+" .alpha._(k_S)b.alpha._(k_L)
.dagger.).delta.(k_L "-" k_S "-"
k_.nu.))+(.differential..alpha./.differential.q)_0 .SIGMA._(k_AS
k_L) (((2.omega._L .omega._AS))/.omega._0)(e_(k_L)""
e_(k_AS))(.alpha._(k_AS) .dagger. b.alpha._(k_L)"+" .alpha._(k_AS)b
.dagger. .alpha._(k_L) .dagger.).delta.(k_L "-" k_AS "+"
k_.nu.)
where H_.gamma.S and H_.gamma.AS are the interaction Hamiltonians
of the Stokes and anti-Stokes branches, respectively.
[0273] The steady state transition rate between the initial, |i,
and final, |f states is given according to Fermi's golden rule,
W_(i.fwdarw.f)=2.pi./|f|H_int|i 2.rho.(.omega._f).
In the simple harmonic oscillator picture, the eigenstates, |n_.nu.
with excitation quanta n_.nu. are acted upon by creation and
annihilation operators to yield the Stokes and anti-Stokes
transition rates
W_(n_.nu.).fwdarw.n_.nu.+1, "and"
W_(n_.nu.).fwdarw.n_.nu.-1.about.n_.nu..
Hence, it is easy to determine n_.nu. from the Raman signal
intensity given a linear dependence.
[0274] Raman intensities from each vibrational level are used to
identify unique vibrational molecular modes and characterize the
material's composition
[0275] The integrated anti-Stokes intensity of a Raman mode is
proportional to the average vibrational quantum number of the mode,
n_.nu.,
I_AS=A(E_R/(h.nu._R))=An_.nu.
where A is the Raman cross section. Normalizing I_AS with respect
to the room temperature Stokes signal of the same mode in addition
to using the Boltzmann distribution,
n_.nu.0=(E_R 0)/(h.nu._R)=1/(e ((h.nu._R)/(kT_0))-1)
where E_R 0 is the room temperature (T_0) energy of the Raman mode.
Generally, h.nu._R>>kT_0. so n_.nu.0=0, and the normalized
anti-Stokes signal is approximately n_.nu.
I_norm.ident.I_AS/(I_R 0)=An_.nu./A(1+n_.nu.0).apprxeq.n_.nu..
By comparing the normalized scattering intensities associated with
different vibrational moved, the distribution of energy over
different molecular modes after infrared excitation may be
obtained.
Stimulated Raman Spectroscopy
[0276] Stimulated Raman intensity is nonlinearly dependent on the
incident intensity of photons but of similar magnitude. Inelastic
scattering of a photon with an optical phonon originating from a
finite response time of the third order nonlinear polarization of a
material is characteristic of Raman scattering. Monochromatic light
propagating in an optical material yields spontaneous Raman
scattering in which some photons are transitioned to new
frequencies. The polarization of scattered photons may be parallel
or orthogonal if the pump beam is linearly polarized. Stimulated
Raman scattering occurs when the scattering intensity of photons at
shifted frequencies is enhanced by existing photons already present
at these shifted frequencies. Consequently, in stimulated Raman
scattering, a coincident photon at a downshifted frequency receives
a gain which may be exploited in Raman amplifiers, for example, or
usefully employed in molecular spectroscopy.
[0277] Stimulated Raman scattering (SRS) has been observed in glass
fibers and Raman gain has been measured in single mode fibers.
Raman amplification became a mature technology with the
availability of sufficiently high-power pump lasers.
[0278] Within a classical electromagnetic framework, the stimulated
Raman scattered signal intensity increases proportionally with the
pump and signal intensities
(dI_s)/dz=g_R I_P I_S
and the Raman-gain coefficient, g_R, which is related to the
spontaneous Raman scattering cross section. Hence, the probability
of Raman scattering is directly related to the photon density in
the pump wave and the Raman cross section.
[0279] The Stokes and pump waves must overlap spatially and
temporally to generate stimulated emission. Since, the Raman
process involves vibrational modes of molecules within a material;
its intensity spectrum determines the material composition. In
amorphous materials, for example, the vibrational energy levels
tend to merge and form bands and the pump frequency may differ from
the Stokes frequency over a wide range. In crystalline materials,
however, the intensity peaks tend to be well-separated as they have
narrow bandwidths.
[0280] The coupled wave equations for forward Raman scattering
include
(dI_S)/dz=g_R I_p I_S-.alpha._S I_S
for Stokes intensities with .alpha._S the Stokes attenuation
coefficient, and
(dI_P)/dz=-.omega._P/.omega._S g_R I_p I_s-.alpha._P I_P
for pump wave intensities where .omega._P and .omega._S are pump
and Stokes frequencies, respectively. For backward scattering,
dI_S/dz.fwdarw.-dI_S/dz. In the absence of loss, these expressions
reduce to
d/dz(I_S/.omega._s+I_P/.omega._P)=0
which embodies the conservation of photon number in Stokes and pump
waves during stimulated Raman scattering processes.
[0281] Stimulated scattering intensity increases when the
stimulated gain exceeds the linear loss which is the source of the
threshold power which must be overcome to initiate stimulated Raman
scattering. In a material system in which forward and backward
scattering occurs, a beat frequency drives molecular oscillations
responsible for increasing the scattered wave amplitude. In turn,
the increasing wave amplitude enhances the molecular oscillations
as part of a positive feedback loop that results in the stimulated
Raman scattering effect. For forward scattering processes, the pump
depletion term is removed,
(dI_P)/dz=-.alpha._p I_P.
[0282] Solving this equation yields I_P(z)=I_0 e (-.alpha._P z)
giving the stimulated Stokes scattering intensity
I_S(L)=I_S(0)e (g_R I_o L_eff-.alpha._P L)
where the effective optical path length is given by
L_eff=(1-e (-.alpha._p L))/.alpha._P.
Stimulated Raman scattering intensifies from scattering events
occurring throughout the optical path length in the material,
making it a useful molecular spectroscopy technology.
Resonance Raman Spectroscopy
[0283] The Raman effect in classical Raman spectroscopy depends
only on the frequency of incident light with scattered intensity
dependence on .nu._0 4 as discussed earlier. If the vibrational
mode of a molecular absorption transition precisely matches the
energy of incident light, the observed scattered intensity may be
as intense as .about..nu._0 6. This resonance Raman effect permits
highly sensitive spectroscopic discrimination of a molecular
species within a complex material medium such as chromophores
within proteins embedded in a biological membrane.
[0284] In resonance Raman spectroscopy, only a small fraction of
molecular vibrational modes are enhanced. In the simplest scenario,
only one electronic state may be resonant. In this case, the
resonant Raman signal is the result of nuclear motion resulting
from distortions of the molecule while transitioning between the
ground state and the excited state in which resonance is induced by
incident light.
[0285] The functional component of most biological chromophores
consist of atoms conjugated with the particular electronic
transition to which resonance Raman spectroscopy is selectively
sensitive. The frequency of measured resonance Raman bands yields
information about the vibrational structure of the electronic
states involved in the transition used for inducing the resonance.
The scattering intensities provide information about the nature of
mode coupling with the electronic transition.
Raman Effect in Vortex Light
[0286] A molecule in vibronic state m subjected to a
plane-polarized incident light of frequency .nu._0 and intensity
I_0 is perturbed into a new vibronic state n. This interaction
causes the frequency of light to shift by .nu._mn=.nu._m-.nu._n and
scatter with a frequency .nu._0+.nu._mn through a solid angle
4.pi.. The scattering intensity during the transition from m to n
is given by
I_mn=(2 6 .pi. 4)/(3c 3)(.nu._0+.nu._mn) 4|_mn| 2
in which the amplitude _mn of the electric field is given by
_mn=1/h
.SIGMA._r((M_m(M_mr))/(.nu._rm-.nu._0)+(M_mr(M_rn))/(.nu._rn+.nu-
._0))
where, m, r and n are quantum numbers of the initial, intermediate
and final energy states E_m, E_r, E_n, respectively.
[0287] Between the amplitude of the electric field strength
=e_ (-2.pi.i.nu._0 t)+ *e (2.pi.i.nu._0 t)
and its amplitude _mn associated with the shifted scattered
radiation induced torque,
M_mn=_mn e (-2.pi.i(.nu._0+.nu._mn)t)+_mn *e
2.pi.i(.nu._0+.nu._mn)t
is a tensor relation that may be expressed in terms of scattering
tensor A_mn=(.alpha._.rho..sigma.)_mn in the form
_mn=A_mn
or in component representation,
(_.rho.)_mn=.SIGMA._.sigma. (.alpha._.rho..sigma.)_mn_.sigma.
while the scattering tensor A_mn may be expressed as
A_mn=1/h .SIGMA._r ((M_rn M_mr)/(.nu._rm-.nu._o)+(M_mr
M_rn)/(.nu._rn+.nu._0))
[0288] Since _mn written in terms dyadic components of the tensor
A_mn includes M_rn M_mr, each .rho..sigma.th matrix element of the
polarizability tensor, .alpha., for a transition from m to n, may
be written in terms of intermediate vibronic states
(.alpha._.rho..sigma.)_mn=1/2.pi. .SIGMA._r
(((M_.rho.)_rn(M_.sigma.)_mr)/(.nu._rm-.nu._0)+((M_.rho.)_mr(M_.sigma.)_r-
n)/(.nu._rn+.nu._0))
[0289] Where (M_.rho.)_mn is the transition matrix between
vibrational levels m and n in the presence of the radiation
operator m _.rho.,
(M_.rho.)_mn=.intg. .PSI._r *m _.rho. .PSI._m d.tau.
[0290] Herein, (M_l)_rn (M_.sigma.)_mr are ordinary products of
scalar vector components) (M_l)_rn and (M_.sigma.)_mr of a unit
vector .alpha._.sigma.. In the three mutually perpendicular
directions spatially fixed l, .sigma.=1,2,3 as follows
_mn 2 = _.rho. ( _ ) _mn 2 = _.rho. _.sigma. = A ^ 6 _.rho.
_.sigma. ( .alpha._.rho..sigma. ) _mn.alpha. _.sigma. 2
##EQU00031##
With an incident intensity, I_0=(c/2.pi.)A 2, then,
I_mn = ( 2 ^ 6 .pi. ^ 4 A ^ 2 ) / ( 3 c ^ 3 ) ( v_ 0 + v_mn ) ^ 4
_.rho. = ( 2 ^ 7 .pi. ^ 5 ) / ( 3 c ^ 3 ) I_ 0 ( v_ 0 + v_mn ) ^ 4
_.rho. . ##EQU00032##
[0291] The total scattering intensity is therefore dependent on the
state of polarization of the exciting light. By averaging over all
positions of .alpha., or averaging over all modes of the scattering
molecule at a fixed incident wave direction and polarization,
(|.SIGMA._.sigma.(.alpha._.rho..sigma.)_mn .alpha._.sigma. |
2).sup.-=1/3 .SIGMA._.sigma.|(.alpha._.rho..sigma.)| 2.
[0292] Finally, for an electron transition from m.fwdarw.n per
molecule an average total intensity of the scattered radiation is
obtained
I_mn=(2 7 .pi. 5)/(3 2 c 4)I_0(.nu._0+.nu._mn) 4 .SIGMA._(.rho.,
.sigma.)|(.alpha._.rho..sigma.)_mn| 2
in which .rho.=x, y, z and .sigma.=x ', y ', z' are independently
the fixed coordinate systems of the molecule for incident and
scattered photons, respectively. Selection Rules for Raman Effect
using Vortex Light
[0293] Of interest to studies of the Raman effect using vortex
light is a particular set of solutions of Maxwell's equations in a
paraxial approximation. Laguerre-Gaussian functions may
mathematically characterize a beam of vortex light in terms of
generalized Laguerre polynomials, L_p l (x), with a Gaussian
envelope. In the Lorentz-gauge, the vector potential of a
Laguerre-Gaussian beam is
A_(l, p)=A_0(.alpha.e _x+.beta.e _y) (2p!/.pi.(|l|+p)!)w_0/w(z)L_LP
|l|((2.rho. 2)/(w 2(z)))(( 2.rho.)/w(z)) |l|e
(il.phi.-i.omega.t+ikz)
in a (.rho., .phi., z) coordinate system in which w(z) is the beam
waist (radius) at which the radial field amplitude goes to 1/e. For
simplicity, only p=0 is typically chosen. In the dipole
approximation, the term, e ikz is negligible, so the radiation
operator of a Laguerre-Gaussian beam may be expressed as
m _.rho.=[A_0(.alpha.e x+.beta.e _y) (1/.pi.!|l|!)w_0/w(z)L_0
i((2.rho. 2)/w 2(z))(( 2.rho.)/w(z)) i e
(il.phi.-i.omega.t)]p+c.c
Here, e i.omega.t is associated with photon emission and e
(-i.omega.t) is associated with photon absorption.
[0294] The following generalized framework for developing a set of
selection rules to measure unique OAM Raman signatures of different
materials applies to the intensity profiles associated with both
stimulated and spontaneous Raman spectroscopy.
[0295] The relationship among irreducible representations of the
phonon, the incident photon, and the scattering photon,
.GAMMA._.alpha., .GAMMA._.rho., and .GAMMA._.sigma., required to
ensure non-vanishing matrix elements of A_(l, p) is
.GAMMA._.alpha. .GAMMA._.rho. .GAMMA._.sigma. .GAMMA._1
such that h_(e, s) .alpha., (M_.rho.)_(g, e), and (M_.sigma.)_(g,
s) are non-zero. Introducing, the Raman tensor
P_.alpha..beta..gamma..delta. (.GAMMA._j .sigma.) having index
.GAMMA._j .sigma. to denote the jth branch of the .sigma.th phonon
to replace the single index .alpha., we similarly replace the
incident photon index, .rho., with (.alpha., .beta.) and the
scattered photon index, .sigma. with (.gamma., .delta.).
[0296] As the interaction of light with matter in Raman scattering
processes leaves the orbital angular momentum of photons
unperturbed the incident and scattered photons may be expressed in
the following respective forms,
(.rho. _1).rho. l e il.phi. "and"(.rho. _s).rho. l e
(-il.phi.).
Then P_.alpha..beta..gamma..delta. (.GAMMA._j .sigma.) may be
determined by the Clebsch-Gordan coefficients for all three
representations
P_(z, _s, _I, z)(.GAMMA.hd --j .sigma.)=(.rho. _S).rho. l e
(-il.phi.)(.rho. _I).rho. l e il.phi..phi._.sigma. j
[0297] For crystalline materials, the special case of forward
scattering reduces 3.times.3 Raman tensors to 2.times.2. In this
case, the Raman tensors for l.gtoreq.2 excitations all have the
same form. So from symmetry considerations, the l-dependence
vanishes for l.gtoreq.2. Since the constants a, b, c, d, and e
depend on l and the symmetry of the crystal, non-zero OAM yields a
.GAMMA..sub.2 phonon for l.gtoreq.2 photon excitation and decouples
the two Raman tensors for the .GAMMA..sub.3 phonon for l.gtoreq.1
photon excitation.
[0298] OAM Raman spectroscopy exhibits the capacity to characterize
the atomic and molecular composition of a crystalline material.
More complicated selection rules are needed to fully obtain an OAM
Raman signature of chiral materials which present their own unique
atomic and molecular symmetry properties.
[0299] In the highly symmetric case of crystalline materials, for
example, the approach is rather straightforward. Given a periodic
lattice potential, electrons in crystal solids may be expressed as
Bloch waves
.psi._(n, k)(r)=e (ikr)u_nk(r)
such that the electron transition moment connecting the ground
state, .psi._(g, k), to the excited state, .psi._(e, k), may be
written
M_(g, e)=.SIGMA._k.intg. .psi._(e, k) *(r)[A_0(.rho. l e il.phi.)p]
.psi._(g, k)(r)dr
The first order Taylor expansion with l=0 is then
(M _.rho.)_(g, e)=(M _.rho.)_(g, e) 0+.SIGMA._(.alpha., S)(h_es
.alpha. Q_.alpha.)/(.DELTA.E_(e, S))(M _.rho.)_(g, e) 0.
[0300] Since h_(e, S) .alpha., Q_.alpha., and .DELTA.E_es depend
only on the properties of the crystal and not l, only M affects
scattering intensities when using vortex light. Subsequently, the
electronic wavefunction and l are left as relative values of
M(l.noteq.0) with respect to M(l=0) for the Raman effect with
vortex light interactions with crystal solids.
[0301] Raman scattering intensity enhancements may be identified by
selecting appropriate values of l such as in the case of zinc
blende crystals, for example, in which a maximum was reported for
l=30 based on symmetry considerations using the approach presented
above. In practice, focusing a laser producing vortex light has
little impact on the intensity enhancement of M given its
similarity to focusing light in an ordinary Raman scattering
measurement.
Polarized Raman Spectroscopy
[0302] Given that the polarizability of molecules varies spatially
with respect to the distribution of molecules in a sample, a
plane-polarized Raman source may be used to characterize the atomic
structure of crystals and molecular structure of polymeric films,
crystals, and liquid crystals.
[0303] Referring now to FIG. 69, polarized Raman techniques involve
a polarizer 6906 between the sample 6904 and the spectrometer 6908
oriented either parallel (II) or perpendicular (.perp.) to the
polarization state of the laser source 6902. As well, polarizing
optics 6910 may be inserted between the laser 6902 and sample 6904
to select an appropriate state of polarization incident on the
sample.
[0304] The symmetry properties of bond vibrations in a molecule are
characterized by polarized Raman spectroscopy by evaluating the
depolarization, .rho., of particular intensity peaks,
.rho. = I .perp. I .parallel. ##EQU00033##
where l_.perp. and I_.parallel. are the Raman spectral band
intensities with polarizations perpendicular and parallel,
respectively, to the state of polarization of the laser source
6902.
[0305] As shown in FIG. 70, information gained by polarized Raman
spectroscopy 7002 can be used to supplement atomic and molecular
information gained by non-polarized Raman spectroscopy 7004. A
single integrated spectroscopy unit 7006 exploiting both polarized
and non-polarized Raman effects using combined results processing
7008 that improves overall quality and amount of information gained
by spectroscopically processing data from a sample using multiple
types of spectroscopic analysis.
Raman Spectroscopy with Optical Vortices
[0306] The typical Raman source is a Gaussian laser operating in
its fundamental mode with an electric field
E ( x , y , z ) = e ^ E 0 exp ( - x 2 + y 2 w 2 ) exp [ - ( kz -
.omega. t ) ] . ##EQU00034##
traveling in the z-direction, where is the polarization vector.
Light produced by such a source has either linear or circular
polarization which are limited to the transverse (x, y) plane with
no electric field component in the z-direction. The induced dipole
moments of interest then are only P.sub.x and P.sub.y.
[0307] A longitudinal mode along the z-direction incident on a
molecule scatters light that completes the picture of the
molecule's polarizability to include P_z. An electric field having
a z-component is a radially-polarized beam with a polarization
vector
=x{circumflex over (x)}+yy={circumflex over (r)}.
[0308] Several methods exist to generate radially polarized fields
having longitudinal components when tightly focused. In Raman
spectroscopy, the induced dipole moment, P.sub.z, is the result of
E.sub.z which may increase the strength of vibrational modes in
addition to generating new vibrational modes previously unobserved
with conventional Raman spectroscopy. As shown in FIG. 71,
information gained by Raman beams endowed with optical vortices
7102 adds a third degree of spectroscopic capability when coupled
with polarized 7104 and non-polarized 7106 Raman spectroscopy in a
combined analysis 7108. Such Raman spectroscopy can also work in
conjunction with incident photons that carry OAM.
THz Spectroscopy
[0309] Terahertz spectroscopy is conducted in the far-infrared
frequency range of the electromagnetic spectrum (FIG. 61) and is
therefore useful for identifying far-infrared vibrational modes in
molecules. THz spectroscopy can provide a higher signal-to-noise
ratio and wider dynamic range than far-infrared spectroscopy due
the use of bright light sources and sensitive detectors. This
provides for selective detection of weak inter- and intra-molecular
vibrational modes commonly occurring in biological and chemical
processes which are not active in IR-spectroscopy. THz spectroscopy
may also be used in conjunction with incident photons that carry
OAM. Terahertz waves pass through media that are opaque in the
visible and near-IR spectra and are strongly absorbed by aqueous
environments (see FIG. 72).
[0310] THz spectroscopy was historically hindered by a lack of
appropriately high powered light sources. However, access to
practical THz spectroscopy in the far-infrared range was permitted
by the generation of THz rays based on picosecond and femtosecond
laser pulses. Today, THz sources include either short pulse mode
(e.g. photoconductive antennas, optical rectifiers) or continuous
wave (CW) mode having a wide range of available output power
(nanowatts to 10 watts).
[0311] Several different types of THz sources are used today to
interrogate biological, chemical and solid state processes. Sources
in the 1-3.5 THz range are frequently used in biology and medicine,
for example, to investigate conformational molecular changes. THz
spectroscopy is used today as frequently as Raman spectroscopy.
Terahertz Time-Domain Spectroscopy
[0312] Terahertz time-domain spectroscopy (THz-TDS) is one of the
most widely used THz techniques which includes coherent emission of
single-cycle THz pulses such as provided by a femtosecond laser.
The detection of these pulses occurs at a repetition rate of about
100 MHz.
[0313] Two dimensional THz absorption properties of samples are
characterized by a THz imaging technique. This technique was
demonstrated in systems designed for THz-TDS based on picosecond
pulses as well as systems utilizing continuous-wave (CW) sources
such as a THz-wave parametric oscillator, quantum cascade laser, or
optically pumped terahertz laser. THz spectroscopy can be used in
conjunction with incident photons that carry OAM.
[0314] THz pulse imaging provides broad image frequency information
between 0.1-5 THz while THz CW imaging may be performed in
real-time, is frequency-sensitive, and has a higher dynamic range
due to significantly higher spectral power density. In both pulse
and CW THz imaging the characteristics of the light source
(coherency, power, and stability) are important. A THz spectrometer
may mechanically scan a sample in two dimensions, but the time of
each scan scales with sample size. Real time THz imaging is often
conducted with an array of THz wave detectors composed of
electro-optic crystals or a pyroelectric camera. Such THz
spectroscopy can be used in conjunction with incident photons that
carry OAM.
[0315] THz imaging suffers from poor resolution as estimated in
terms of its diffraction limit which is less than a millimeter and
from low transmission through an aperture resulting in low
sensitivity. To exceed the diffraction limitation near-field
microscopy is used to achieve sub-wavelength resolution, though low
transmission remains an issue.
Fluorescence Spectroscopy
[0316] Perturbed by incident light, electrons in molecules at room
temperature are excited from the lowest vibrational energy level
7302 of the electronic ground state to either the first (S_1) 7304
or second (S_2) 7306 vibrational state (FIG. 73) and may occupy any
one of several vibrational sub-levels. Each vibrational sub-level
has many neighboring rotational energy levels in such close
proximity that inter-sub-level energy transitions are almost
indistinguishable. Consequently, most molecular compounds have
broad absorption spectra with the exception of those having
negligible rotational characteristics such as planar and aromatic
compounds.
[0317] In fluorescence spectroscopy, molecules absorb energy from
incident photons, obtain a higher vibrational energy sub-level of
an excited state (S_1 or S_2), then lose their excess vibrational
energy through collisions and return to the lowest vibrational
sub-level of the excited state. Most molecules occupying an
electronic state above S_2, experience internal conversion and
decay by collision through the lowest vibrational energy sub-level
of the upper state to a higher vibrational sub-level of a lower
excited state having the same energy. The electrons continue to
lose energy until they occupy the lowest vibrational energy
sub-level of S_1 7308. The decay of the molecule into any
vibrational energy sub-level of the ground state causes the
emission of fluorescent photons.
[0318] If the absorption and emission process differs from this
sequence, the quantum efficiency is less than unity. The "0-0"
transition from the lowest vibrational ground state sub-level to
the lowest vibrational S_1 sub-level 7308 is common to both the
absorption and emission phenomena while all other absorption
transitions occur only with more energy than any transition in the
fluorescence emission. The emission spectrum subsequently overlaps
the absorption spectrum at the incident photon frequency
corresponding to this "0-0" transition while the rest of the
emission spectrum will have less energy and equivalently occurs at
a lower frequency. The "0-0" transition in the absorption and
emission spectra rarely coincide exactly given a small loss of
energy due to interaction of the molecule with surrounding solvent
molecules.
[0319] Hence, distributions of vibrational sub-levels in S_1 and
S_2 are very similar since incident photon energy doesn't
significantly affect the shape of the molecule. Energy differences
between bands in the emission spectrum will be similar to those in
the absorption spectrum and frequently, the emission spectrum will
be approximately a mirror image of the absorption spectrum. The
shape of the emission spectrum is always the same despite an
incident photon frequency shift from that of the incident radiation
since the emission of fluorescent photons always occurs from the
lowest vibrational energy sub-level of S_1. If the incident
radiation intensity yielding excitation remains constant as the
frequency shifts, the emission spectrum is considered a corrected
excitation spectrum.
[0320] The quantum efficiency of most complex molecules is
independent of the frequency of incident photons and the emission
is directly correlated to the molecular extinction coefficient of
the compound. In other words, the corrected excitation spectrum of
a substance will be the same as its absorption spectrum. The
intensity of fluorescence emission is directly proportional to the
incident radiation intensity.
[0321] Fluorescence spectroscopy results in emission and excitation
spectra. In emission fluoroscopy, the exciting radiation is held at
a fixed wavelength and the emitted fluorescent intensity is
measured as a function of emission wavelength. In excitation
fluoroscopy, the emission wavelength is held fixed and the
fluorescence intensity is measured as a function of the excitation
wavelength. This type of fluorescence spectroscopy may also be used
in conjunction with incident photons that carry OAM. Performing
both emission and excitation spectra together yields a spectral map
of the material under interrogation. Materials of interest may
contain many fluorophores, and different excitation wavelengths are
required to interrogate different molecules as shown in FIGS. 74A
and 74B for the absorption and emission spectra for tryptophan,
elastin, collagen, nicotinamide, adenine dinucleotide (NADH) and
flavins.
[0322] Fluorescence spectrometers analyze the spectral distribution
of the light emitted from a sample (the fluorescence emission
spectrum) by means of either a continuously variable interference
filter or a monochromator. Monochromators used in more
sophisticated spectrometers select the exciting radiation and
analyze the sample emission spectra. Such instruments are also
capable of measuring the variation of emission intensity with
exciting wavelength (the fluorescence excitation spectrum).
[0323] One advantage of fluorescence spectroscopy compared to
equivalent absorption techniques is that the sample may be
contained in simple test tubes rather than precision cuvettes
without appreciable loss in precision because of the geometrical
configuration of simple fluorimeters in which only the small
central region of the cuvette is interrogated by the detector.
Hence, the overall size of the cuvette is less important.
[0324] Sensitivity of fluorescence spectroscopy depends largely on
the properties of the measured sample and is typically measured in
parts per billion or trillion for most materials. This remarkable
degree of sensitivity permits reliable detection of very small
sample sizes of fluorescent materials (e.g. chlorophyll and
aromatic hydrocarbons).
[0325] Fluorescence spectroscopy is exceptionally specific and less
prone to interference because few materials absorb or emit light
(fluoresce) and rarely emit at the same frequency as compounds in
the target material.
[0326] Fluorescence measurements scale directly with sample
concentration over a broad frequency range and can be performed
over a range of concentrations of up to about one six orders of
magnitude without sample dilution or alteration of the sample cell.
Additionally, the sensitivity and specificity of fluoroscopy
reduces or eliminates the need for costly and time-consuming sample
preparation procedures, thus expediting the analysis. Overall,
fluoroscopy represents a low-cost material identification technique
owing to its high sensitivity (small sample size requirement).
Pump-Probe Spectroscopy
[0327] Pump-probe spectroscopy is used to study ultrafast phenomena
in which a pump beam pulse perturbs atomic and molecular
constituents of a sample and a probe beam pulse is used to
interrogate the perturbed sample after an adjustable period of
time. This optical technique is a type of transient spectroscopy in
which the electronic and structural properties of short-lived
transient states of photochemically or photophysically relevant
molecules may be investigated. The resulting excited state is
examined by monitoring properties related to the probe beam
including its reflectivity, absorption, luminescence, and Raman
scattering characteristics. Electronic and structural changes
occurring within femto- to pico-second timeframes may be studied
using this technique.
[0328] Generally, pump-induced states represent higher energy forms
of the molecule. These higher energy molecular forms differ from
their lowest ground state energy states including a redistribution
of electrons and/or nuclei.
[0329] A basic pump probe configuration is shown schematically in
FIG. 75. A pulse train generated by a laser 7502 is split into a
pump pulse 7506 and a probe pulse 7508 using a beamsplitter 7504.
The pump pulse 7506 interacts with the atoms and molecules in a
sample 7510. The probe pulse 7508 is used to probe the resulting
changes within the sample after a short period of time between the
pulse train and the probe pulse train. By changing the delay time
between pulse trains with an optical delay line, a spectrum of
absorption, reflectivity, Raman scattering, and luminescence of the
probe beam may be acquired after the sample to study the changes
made by the pump pulse train at detector 7512. It is possible to
obtain information concerning the decay of the pump-induced
excitation by monitoring the probe train 7508 as a function of the
relative time delay. The probe train 7508 is typically averaged
over many pulses and doesn't require a fast photodetector 7512. The
temporal resolution of measurements in pump-probe spectroscopy is
limited only by the pulse durations of each train. In general, the
uncertainty in timing must be smaller than the timescale of the
structural or electronic process induced by the pump train.
[0330] In two-color pump-probe spectroscopy, the pump 7506 and
probe 7508 beams have different wavelengths produced by two
synchronized sources. While this technique provides additional
capabilities in ultrafast spectroscopy, it's essential to ensure
precise source synchronization with a very low relative timing
jitter.
[0331] In comparison with spontaneous Raman scattering intensities,
the scattered intensities provided by a pump-probe Raman
spectroscopy technique may be tremendously enhanced with different
pump and probe frequencies, .OMEGA. and .omega., as shown in FIG.
76. The frequency of the pump beam is changed, while the frequency
of the probe beam is fixed. The pump beam is used to induce Raman
emission, while the probe beam serves to reveal Raman modes. Both
the pump and the probe beam traverse a Raman-active medium in
collinearity. When the difference between the pump and probe
frequencies coincide with a Raman vibrational mode frequency, v, of
the medium, the weak spontaneous Raman light is amplified by
several orders of magnitude (10-10.sup.4) due to the pump photon
flux. Gain is achieved as shown in FIG. 76.
[0332] The pump beam is essentially engineered to provide a variety
of perturbative excitations within a wide range of samples.
Pump-probe spectroscopy is therefore applicable to use within the
context of other spectroscopy techniques including the use of a
pump beam endowed with orbital angular momentum as discussed in the
next section.
Orbital Angular Momentum (OAM) Spectroscopy
[0333] Chiral optics conventionally involved circularly polarized
light in which a plane polarized state is understood as a
superposition of circular polarizations with opposite handedness.
The right- and left-handedness of circularly polarized light
indicates its spin angular momentum (SAM), .+-.h in addition to the
polarization one can use the helicity of the associated
electromagnetic field vectors. Its interaction with matter is
enantiomerically specific. The combined techniques would have
specific signatures for different materials.
[0334] As described more fully herein above, optical vortices
occurring in beams of light introduce helicity in the wavefront
surface of the electromagnetic fields and the associated angular
momentum is considered "orbital". Orbital angular momentum (OAM) of
photonic radiation is frequently called a "twisted" or "helical"
property of the beam. Most studies of OAM-endowed light
interactions with matter involve achiral molecules.
[0335] Delocalized OAM within solid materials associated with the
envelope wavefunction in a Bloch framework, which may be spatially
macroscopic in extent, may be distinguished from local OAM
associated with atoms. The latter is associated with the Lande
g-factor of electronic states and part of the effective spin while
the former is of interest to orbitally coherent systems (e.g.
quantum Hall layers, superconductors, and topological insulators).
Development of these techniques represents opportunities to improve
our understanding of scattering and quantum coherence of chiral
electronic states, with potential implications for materials
discovery and quantum information. To this end, theoretical
frameworks describing the OAM-matter interaction, such as with
dielectric materials are useful.
[0336] OAM-endowed beams of light have been used to induce such
delocalized OAM-states in solids using a time-resolved pump-probe
scheme using LG beams in which the OAM-sensitive dichroism of bulk
n-doped (3.times.10.sup.16 cm.sup.-3 Si) and undoped GaAs (held in
a cryostat at 5K) is exploited. Using this method, "whirlpools" of
electrons were induced and measured with a time-delayed probe beam
whose OAM components were detected in a balanced photodiode bridge.
The study demonstrates that time-resolved OAM decay rates
(picoseconds to nanoseconds) are doping dependent, differed from
spin and population lifetimes, and longer than anticipated as
described in M. A. Noyan and J. M. Kikkawa, "Time-resolved orbital
angular momentum spectroscopy," Appl. Phys. Lett. 107 032406
(2015), which is incorporated herein by reference in its
entirety.
[0337] A simple pump-probe OAM spectroscopy instrument is shown
schematically in FIG. 77 in which the OAM pump beam 7702 is an
l=.+-.1 Laguerre-Gaussian beam cycled between l=+1 and l=-1 at some
frequency, .nu._l. The pump beam 7702 perturbs target molecules in
the sample 7704 while a direct probe beam 7406 is used to
interrogate the resulting perturbation. The sample may be a
crystalline solid, amorphous solid, liquid, biological, or
inorganic.
[0338] The interaction of light exhibiting OAM, an azimuthal
photonic flow of momentum, with chiral molecules is the subject of
several recent theoretical and experimental reports. On one hand,
the strength of the interaction has been conjectured as negligible,
while on the other hand, not only does such an interaction exist,
it may be stronger than the interactions occurring in conventional
polarimetry experiments in which the direction of linearly
polarized light incident on a solution is rotated by some angle
characteristic of the solution itself. A few limited experimental
studies have suggested that the former theoretical body of work is
correct--that such an interaction is negligible.
[0339] Nonetheless, a variety of light-matter interactions
involving OAM-endowed optical beams indicate a broad range of
possibilities in spectroscopy including OAM transfer between
acoustic and photonic modes in optical fibers, OAM-endowed Raman
sideband generation, and the manipulation of colloidal particles
manipulation with optical OAM "tweezers".
OAM Spectroscopy of Chiral Molecules
[0340] Recent experiments using Laguerre-Gaussian (LG) beams of
varying integer azimuthal order, l, traveling through a short
optical path length of various concentrations of glucose, support
the theoretical body of work suggesting the existence of
measureable OAM light-matter interactions. These experiments
suggest that not only does the interaction exist, but it appears to
be stronger than with polarimetry since perturbations of the OAM
beam occur within a very short optical path length (1-3 cm) than
commonly required in conventional polarimetry studies (>10 cm)
to obtain a measureable perturbation of the linear state of
polarization.
[0341] The Gaussian beam solution to the wave equation and its
extension to higher order laser modes, including Hermite-Gaussian
(HG) and commonly studied in optics labs. Of particular interest,
LG modes exhibit spiral, or helical, phase fronts. In addition to
spin angular momentum, the propagation vector includes an orbital
angular momentum (OAM) component often referred to as
vorticity.
[0342] A spatial light modulator (SLM) is frequently used to
realize holograms that modulate the phase front of a Gaussian beam
and has renewed interest in engineered beams for a variety of
purposes.
[0343] The expression for the electric field of an LG beam in
cylindrical coordinates is
u ( r , .theta. , z ) = [ 2 pl 1 + .delta. .sigma. , m .pi. ( + p )
! ] 1 2 exp { j ( 2 p + + 1 ) [ .psi. ( z ) - .psi. 0 ] } 2 r w 2 (
z ) L p ( 2 r 2 w 2 ( z ) ) exp [ - j k r 2 2 q ( z ) + .theta. ]
##EQU00035##
[0344] with w(z) the beam spot size, q(z) a complex beam parameter
comprising evolution of the spherical wavefront and spot size, and
integers p and l index the radial and azimuthal modes,
respectively. The exp(il.theta.) term describes spiral phase
fronts. A collimated beam is reflected off the SLM appropriately
encoded by a phase retarding forked grating, or hologram, like the
one shown in FIGS. 15A-15D. The generating equation for the forked
hologram may be written as a Fourier series,
T ( r , .PHI. ) = m = - .infin. .infin. t m exp [ - m ( 2 .pi. D r
cos .PHI. - l .PHI. ) ] , ##EQU00036##
where r and .phi. are coordinates, l is the order of vorticity, and
D is the rectilinear grating period far from the forked pole.
Weights, t_m, of the Fourier components may be written in terms of
integer-order Bessel functions,
t.sub.m=(-i).sup.mJ.sub.m(k.beta.)exp(ik.alpha.).
where k.alpha. and k.beta. bias and modulate the grating phase,
respectively. Only a few terms are needed to generate OAM beams,
such as -1.ltoreq.m.ltoreq.1,
T ( r , .PHI. ) = 1 2 - 1 2 sin ( 2 .pi. D r cos .PHI. .PHI. - l
.PHI. ) . ##EQU00037##
[0345] As shown in FIG. 78 for OAM mode orders l=5, 6, and 7
propagated through 3 cm cuvettes containing different
concentrations of glucose, the OAM signature was found to be
nonlinear with respect to concentration. Though this preliminary
data is noisy, the trend persists over several OAM orders and was
repeatable day to day and after several setup re-alignments and
other changes made for convenience.
[0346] Glucose exhibits a broad optical absorption band at
.about.750 nm with FWHM .about.250 nm. A stronger OAM response was
observed at 543 nm where absorbance is four times smaller than at
633 nm. This suggests an interaction based on the real part of
susceptibility, Z ', rather than its imaginary part, X''. In
separate glucose polarimetry experiments with cuvettes as long as
20 cm, a 50% larger specific rotation was measured at 543 nm than
at 633 nm. Consistent with previous OAM polarimetry studies with
chiral molecules in solution no discernable polarization state
changes were observed with OAM beams through 3 cm or shorter
samples.
[0347] While glucose is known to have polarimetric responses at
these wavelengths the concentration-path length product, cl, was
too small in this OAM study to produce measureable shifts in the
state of polarization. The observed topological changes reported
using OAM-endowed beams suggests the interaction of OAM beams with
chiral molecules is more pronounced than interactions associated
with traditional polarimetry. OAM beam interactions with chiral
molecules may lead to new metrological techniques and perhaps a
richer understanding of subtle light-matter interactions. Of
particular interest is the interaction of light with molecules
exhibiting varying degrees of chirality, a subject taken up in the
next section.
Molecular Chirality
[0348] The chirality of a molecule is a geometric property of its
"handedness" characterized by a variety of spatial rotation,
inversion, and reflection operations. Conventionally, the degree of
chirality of molecules was starkly limited to a molecule being
either "chiral" or "achiral" in addition to being "left-handed" or
"right-handed". However, this binary scale of chirality doesn't
lend well to detailed spectroscopic studies of millions of
molecular systems that may be studied. In its place, a continuous
scale of 0 through 100 has been implemented for the past two
decades called the Continuous Chirality Measure (CCM). Essentially,
this continuous measure of chirality involves the Continuous
Symmetry Measure (CSM) function,
S ' ( G ) = 1 n i = 1 n P i - P ^ i 2 ##EQU00038##
where G is a particular symmetry group, P.sub.i are the points of
the original configuration, {circumflex over (P)}.sub.i are the
corresponding points in the nearest G-symmetric configuration, and
n is the total number of configuration points.
[0349] The objective is to identify a point set, P.sub.i, having a
desired G-symmetry such that the total normalized displacement from
the original point set P.sub.i is a minimum. The range of symmetry,
0.ltoreq.S'(G).ltoreq.1, may be expanded such that S=100S'. The
advantages of CCM over other chiral measure schemes include its
ease of application to a wide variety of chiral structures
including distorted tetrahedra, helicenes, fullerenes, frozen
rotamers, knots, and chiral reaction coordinates, as well as being
a measured without reference to an ideal shape. Unique chirality
values are made with reference to nearest symmetry groups (.sigma.
or S.sub.2n), thus allowing for direct comparison with a wide
variety of geometric.
[0350] Yet, since the new technique described above discusses the
use of Stimulated Raman or Resonant Raman spectroscopy with vector
beams (i.e., beams with "twistedness" plus polarization), the
technique can equally be applied to both chiral and non-chiral
molecules.
Raman with Orbital Angular Momentum
[0351] The effect of orbital angular momentum on the Raman
scattering spectra of glucose has been investigated. Changes have
been observed in the Raman spectra, in particular at 2950 cm.sup.-1
with L=2 (helical beam) as compared to L=0 (Gaussian beam). The
innovation is that if the sugar molecules possess some types of
chiral symmetry 7908 than there may be a differential signal 7902
(FIG. 79) using OAM 7904 and Raman 7906 spectroscopy. The Raman
spectra of glucose, sucrose and fructose have already been
collected for the three laser wavelengths 488, 514.5 and 632.8 nm
from argon-ion and helium neon laser sources, the signals have been
tabulated and the agreement of each vibration is justified with the
other two laser lines. No resonances were observed as would be
expected since there is no direct electronic absorption with these
energies. The Raman spectra, however, are sensitive to local and
global symmetries of the molecule at any wavelength. Differential
Raman signals will give fundamental information about the
interaction of a chiral electromagnetic field with the sugar
molecules, as well as potentially lead to a selected symmetry
resonance for low level glucose detection in the blood.
[0352] The system used for these measurements is a confocal
microscope attached to a 75 cm single stage spectrometer using a
grating blazed at 500 nm and 1200 lines/mm groove density. The
microscope objective used was 10.times. magnification. To generate
the OAM beam with angular momentum value L=2, a Q plate was
incorporated into the system.
[0353] Referring now to FIG. 80 there is illustrated the alignment
procedure. A linear polarizer is inserted at step 8002 into the
beam path and rotated at step 8004 until maximum transmission
intensity is achieved. A Q-plate is inserted at step 8006 into the
beam path and locates at step 8008 the center that produces the OAM
beam (by observation of the donut). The circular polarizer is
inserted at step 8010 before the Q-Plate. The linear polarizer is
placed at step 8012 after the Q-plate to observe the 4 lobed
structure. Finally, the circular polarizer is rotated at step 8014
until the output from final linear polarizer shows donut for all
angles of final linear polarization. This procedure is iterative
also adjusting applied voltage to Q-plate (appx 4 Volts) and the
square wave driving frequency (appx 2 KHz). The measurements are
taken without the final linear polarizer.
[0354] The resulting spectra with L=2 along with a spectra with L=0
(no elements in the beam path) are shown in FIGS. 81 and 82, both
normalized to the maximum value which for both cases is the Raman
signal near 2800 cm.sup.-1. From these measurements it does show
that there are differential intensities between the two different
excitations. At 400 and 550 cm.sup.-1 there is almost a 50 percent
increase in scattering intensity while the L=2 spectrum shows a few
additional shoulders of each of these lines. Most pronounced is the
intensity ratio of the doublet around 2950 cm.sup.-1.
[0355] The Raman system used for these measurements is alignment
restricted. The incorporation of the additional waveplates causes
slight walk-off which leads to significant collection intensity
drop in the confocal system. Presumably, normalization would
eliminate any alignment intensity issues, however signal to noise
suffers and longer integrations are required. Long integration
times are not always possible or feasible.
[0356] These measurements need to be repeated for glucose and also
done for fructose. Also needed to be checked is the response to
pure circular polarization without OAM. We should be able to access
the alignment and optimize for the Q-plate operation. Also to do is
use L=1 value and L=20 values of OAM. With promising results, we
will use a quarter waveplate for 488 nm as this laser produces the
best spectra in the shortest acquisition times on the system.
[0357] Although the higher energy Raman signals are not unique to
glucose as they represent generic carbon and carbon hydrogen bonds
present in many organic systems, it may prove to be unique to
chiral systems. Additionally, the lower energy modes that are more
unique to glucose may show better differentiation with OAM once the
system is better optimized for Q-plates.
Optical Activity with Single Crystal Rock Candy
[0358] Optical activity of sugar molecules is well studied and is a
result of the chiral symmetry of the molecule which leads to the
polarization of the sugar system imparting a small rotation of the
incident light, therefore the final transmitted beam will have a
rotation dependent on the concentration of molecules present.
Experiments have been started in order to develop a versatile and
sensitive system for the detection of polarization changes via
transmission or reflection of materials using orbital angular
momentum. This system is best suited with the use of the SLM so
that any type of beam can in principle be generated. As a starting
point, we have obtained rock candy which shows high crystallinity
and regular cleavage planes of the samples which are few mm thick
each. These candy samples can be polished to have an optical
quality finish on the surfaces, however interior defects so far
have prevented clean transmission measurements and the signal is
collected as forward scatter. The crystals cleave into 3 pieces
showing the clear symmetry of the planes of the crystal, the z-axis
of the crystal is oblique to the cleavage planes. As we begin these
measurements, we are also comparing data to the Q-plate outputs as
well. This measurement system will become the optical system for
balanced and lock-in detection for future polarization sensitive
measurements and the stimulated Raman measurements.
[0359] Multiple monitor access is needed for the SLM on properly
configured computers capable of running the SLM, Matlab and video
capture simultaneously.
[0360] Referring now to FIG. 81, the output of a HeNe laser is
chopped around 1 kHz and sent into a single mode fiber. The output
is collimated with two biconvex lenses, sent through a half wave
plate to adjust the polarization incident onto the Hamamatsu LCOS
SLM 8102 with an angle of incidence of <10 degrees per operation
specifications of SLM. The SLM 8102 displays forked diffraction
grating or spiral phase pattern holograms generated using the
MATLAB code in order to generate the desired OAM beam. The
reflected beam carries OAM and a characteristic "donut" shape is
seen, with zero intensity along the beam axis. This beam is then
sent through a pair of crossed polarizers 8104 and to the detector
8106 for lock-in detection. We will also explore experimental
system which incorporates the use of a balanced detector.
[0361] Experiments have shown a shift of approximately 20 degrees
in the intensity curve for these polished sugar crystals. A series
of measurements are taken once the detection scheme is finalized.
These include: [0362] 1. Optical activity through the entire
polished crystal. [0363] 2. Optical activity through each of the
cleaved pieces independently to investigate if there is
additive/subtractive effects of optical activity for different
cleavage directions and if any of the directions are sensitive to
OAM.
Raman Detection of Glycated Protein
[0364] Hb and Hb-A1c a proteins by Raman spectroscopy using OAM may
also be investigated. Mammalian blood is considered as connective
tissue because of its cellular composition and due to its embryonic
origin and also due to the origin and presence of colloidal
proteins in its plasma. Red Blood cells and Plasma proteins are the
major constituents of blood. These connective tissue components are
targets for metabolic stress under disease conditions and result in
the chemical alterations. All the blood components are subjected to
excessive metabolic stress under hyperglycemic states. Blood acts a
primary transporter of nutrients, gases and wastes. Blood plasma
acts as a primary carrier for glucose to the tissues. Normal
pre-prandial plasma glucose levels are 80 mg/dl to 130 mg/dl and
normal postprandial plasma glucose is <180 mg/dl. The Renal
Threshold for Glucose (RTG) is the physiologic maximum of plasma
glucose beyond which kidneys fail to reabsorb the glucose and get
excreted in urine. This is a condition called glycosuria.
Glycosuria is the key characteristic of Diabetes mellitus (DM).
High plasma glucose in DM will cause increased levels of
Glycosylated Hemoglobin also known as HbA1c. Under normal
physiological conditions HbA1c levels are <7%, this also
expressed as eAG which should be below 154 mg/dl in Normo-glycemic
condition.
Glycation of Plasma Proteins in DM
[0365] Glycation is defined as the non-enzymatic random nonspecific
covalent linking of glucose or other hexose sugar moieties to the
proteins. Under normal blood glucose levels in healthy individuals
will have levels <7% Glycated Hemoglobin (HbA1c) in the blood,
however under hyperglycemic conditions like DM, its levels will
increase. Higher blood glucose levels can induce glycation of other
major proteins of blood plasma like albumin.
Advantages of Measurement of Glycated Proteins in DM:
[0366] Measurements of blood glucose levels only provide the
information about the glycemic status of a subject at a given
moment, i.e. a diabetic person with uncontrolled blood sugar levels
for several months may yield normal blood glucose level if he/she
gets the test under fasting state or with low carbohydrate intake
on a given day. However the measurement of Glycated hemoglobin
(HbA1c) levels in blood yield the information about average blood
sugar levels in patient for past 2 to 3 months. Therefore it has
become a standard clinical practice since past decade to measure
Glycated Hemoglobin in patients with DM with the development
sensitive and reliable laboratory analyses. We propose the use of
Raman spectroscopic studies on Diabetic blood and its components
for the detection of specific Raman finger prints that may result
from non-enzymatic glycosylation of key blood proteins Hemoglobin,
plasma albumin and others in its native and altered physical
states. The process of glycation in proteins induces the chemical
alterations, structural modifications, conformational changes. Any
or all of these can result in special Raman spectral changes which
can used as a clinical marker.
[0367] Measurements were carried out with a small benchtop
OceanOptics Raman system with 532 nm excitation.
Raman spectroscopy of Tryptophan:
[0368] The Hemoglobin (tetramer) has 6 residues of Tryptophan
therefore Hemoglobin is a fluorescent protein. Tryptophan can
undergo glycation and result in conformational changes in
Hemoglobin. The tryptophan changes can be identified by using Raman
studies (Masako Na-G ai et al. Biochemistry, 2012, 51 (30), pp
59325941) which is incorporated herein by reference. In order to
understand the glycation induced Raman spectral changes in
Tryptophan residues Raman spectra is obtained from analytical grade
amorphous Tryptophan using 532 nm OceanOptics Raman
Raman Spectra of Proteins:
[0369] Solid amorphous powders of albumin and Glycated albumin
samples were subjected to Raman measurements using a OceanOptic 532
nm Raman system and the confocal Raman system using 488, 514.5 and
632.8 nm. No Raman signal was observed from these samples, and
therefore we need to retest in solution at a physiologic pH of
7.4.
[0370] The next steps are:
[0371] 1. NIR Raman: Blood and its components have intense
fluorescence in visible range so NIR Raman may help reduce
fluorescence and get good Raman signals from target protein
molecules.
[0372] 2. OceanOptics 532 nm Raman: This can be used detect some of
Glycation derivatives in blood. This needs normal and diabetic
blood either from human subjects or animal models. And also
Reference spectra of synthetic glycation products can be obtained
by using this system, which can later be compared with the Raman
signal from blood samples.
[0373] 3. In Vivo Animal model: For future experiments to be
successful for in vivo blood glucose and diabetes testing, the
Raman measurements need to be carried out in a rat diabetes animal
model.
OAM with Raman for Food Freshness, Spoilage, and Organic
Detection
[0374] Another aspect that will be investigated is food safety
concerns due to spoilage of meats, produce, diary, and grains and
determination if labeled food is organic using Raman and OAM.
Public and individual concern led to both governmental regulation
and commercial requirements of quality, stability, and safety of
food storage periods. Moreover, food deterioration resulting in
food spoilage leads to not only health issues but also economic
loss to food manufacturing and related industries. Thus, minimizing
food spoilage, determining food freshness, or maximizing shelf life
of food is desired.
[0375] Moreover, in 2000, the U.S. Department of Agriculture
("USDA") established guidelines and national standards for the term
"organic." For example, organic food, as defined by USDA
guidelines, means that food must be produced without sewer-sludge
fertilizers, synthetic fertilizers and pesticides, genetic
engineering, growth hormones, irradiation, and antibiotics.
[0376] The traditional physical characteristics of food spoilage,
such as unpleasant smells, unpleasant tastes, color changes,
texture changes, and mold growth, manifest well after biochemical
processes have occurred that impair food quality or safety. As a
result, they are not adequate indicators of determining acceptable
criteria to use for food freshness, preservation, and spoilage.
[0377] Thus, research to date includes the identification of
so-called "biomarkers" of food spoilage. This research includes
identification of the biochemical mechanisms that produce certain
chemical by-products that are associated with the physical
characteristics of food spoilage. These mechanisms can be physical
(e.g., temperature, pH, light, mechanical damage); chemical (e.g.,
enzymatic reaction, non-enzymatic reaction, rancidity, chemical
interaction); microorganism-based (e.g., bacteria, viruses, yeasts,
molds); or other (e.g., insects, rodents, animals, birds).
[0378] One aspect of the investigation is to use OAM and Raman
techniques to identify these so-called biomarkers and their
associated concentrations to better determine shelf life of basic
food categories. Additionally, another aspect of the invention is
to investigate the chemicals used that would fail to qualify
foodstuffs as "organic." For example, the Table 1 below shows
several researched biochemical processes and chemical by-products
associated with food spoilage mechanisms associated with common
food groups:
TABLE-US-00001 TABLE 1 Food Category/ Biochemical Process Mechanism
Spoilage Action Resulting Biomarker Oxidation Light Reversion
Flavor of Soybean 2-pentyl furan Oxidation Light Sunlight flavor in
milk dimethyl disulfide, 2- butanone, ethanol, diacetyl, n-butanol
Oxidation Light Loss of Riboflavin, Vitamins vitamin D-5, 6 ep25 D,
E, and C oxide Oxidation Light Greening of Potato alpha-solanine,
alpha- chaconine Oxidation Decay meat and diary (fats, oils,
aldehydes lipids) Enzymatic Decay Chicken/Meat dimethylsulfide,
dimethyl disulfide, dimethyl trisulfide, dimethyl tetrasulfide,
hydrogen sulfide, ethanol, 3-methyl-1-butanol, acetic acid,
propanioc acid, methanethiol, free fatty acids (FFAs) Enzymatic:
Decay Fruits, Vegatables, Meat, biogenic amines (tyraimine,
Decarboxylation of free Fish, Poultry putrescine, cadaverine, amino
acids (natural histamine) fermentation or via contimation of
microorganisms) Enzymatic Decay Vegatables (loss of vitamin ascrbic
acid, oxidase C) Enzymatic Decay Milk, oils (hydrolytic lipase,
glycerol, free fatty rancidity) acids (FFAs), 3-(E)-hexenal, 2-(E)-
hexenal Enzymatic Decay Vegatables (loss of vitamin lipoxygenase A)
Enzymatic Decay Fruits (loss of pectic petic enzymes substances,
i.e., softing) Enzymatic Decay Fruits (browning) peroxidases
(polyphenol oxidase, o-diphenol, monophenol, o-quinone) Enzymatic
Decay Fruits, Vegatables melanin (browning, sour flavor, vitamin
loss) Enzymatic Decay Eggs, Crab, Lobster, Flour proteases
(reduction of shelf life, overtenderization, reduction in gluten
network formation) Enzymatic Decay Meats, Fish thiaminase Microbial
Bacteria Carbohydrates alcoholic (ethanol, CO2); (fermentation)
homofermentative lactic acid (lactic acid); heterofermentative
lactic acid (lactic acid, acetic aci, ethanol, CO2); propionic acid
fermentation (propionic acid, aetic acid, CO2); butyric acid
fermentation (butyric acid, acetic acid, CO2, H2); mixed acid
fermentation (lactic acid, acetic acid, CO2, H2, ethanol);
2,3-butanediol fermentation (CO2, ethanol, 2,3- butanediol, formic
acid) Microbial Bacteria Degradation of N- (H2S, methyl mercaptns,
Compounds indole, cadaverine, putrescine, histamine) Microbial
bacteria Fish (odor) trimethylamine Microbial Bacteria Lipids
aldehyde, ketones Microbial Bacteria Pectin Degradation
polygalcturonic acid, galacturonic acid, methanol Fishy Odor Decay
Meat, Egg, Fish trimethylamine Garlic odor Decay Wine, Fish, Meat,
Milk dimethyl trisulfide Onion odor Decay Wine, Fish, Meat, Milk
dimethyl disulfide Cabbage odor Decay Wine, Fish, Meat, Milk
dimethyl sulfide Fruity odor Decay Milk, Fish, Wine esters Potato
odor Decay Meat, Egg, Fish 2-methoxy-3- isopropylprazine Alcoholic
odor Decay Fruit juices, Mayonnaise ethanol Musty odor Decay Bread,
Wine tricholoranisole Cheesy odor Decay Meat diacetyl, acetoin
Medicinal odor Decay Juice, Wine 2-methoxy phenol Souring Decay
Wine, Beer, Dairy acetic acid, lactic acid, citric acid Slime Decay
Meat, Juices, Wine polysaccharide Curdling Decay Milk lactic acid
Holes Decay Hard cheese carbon dioxide
[0379] A person skilled in the art would be well aware of various
other mechanisms and biochemical indicators evidencing food
spoilage of common foodstuffs, including other reactions or
volatile or non-volatile organic compound (VOC) by-products
associated with food spoilage. Likewise, a person skilled in the
art would be well aware of the chemicals and additives that do not
qualify food as organic, whether investigating grains, diary,
produce, or meats.
[0380] Traditional spectroscopy techniques are not adequate to
identify in real-time or adequate concentration these bio-markers
in any meaningful manner to determine shelf life of the food sample
or organic nature of the food in question. The present
investigation and invention will employ Raman and OAM techniques
described above to classify, identify, and quantify the various
bio-markers in the table above and the common chemicals that do not
qualify food as organic as defined in federal regulations.
[0381] Such techniques are equally applicable whether the biomarker
or chemical is a chiral or non-chiral molecule. Such data can then
be correlated to concentration of degradation of the sampled food
group to determine minimum and maximum concentrations acceptable to
food freshness, spoilage, organic quality, and safety.
Ince-Gaussian Spectroscopy
[0382] Another type of spectroscopic technique that may be combined
with one or more other spectroscopic techniques is Ince-Gaussian
Spectroscopy. Ince Gaussian (IG) beams are the solutions of
paraxial beams in an elliptical coordinate system. IG beams are the
third calls of orthogonal Eigen states and can probe the chirality
structures of samples. Since IG modes have a preferred symmetry
(long axis versus short axis) this enables it to probe chirality
better than Laguerre Gaussian or Hermite Gaussian modes. This
enables the propagation of more IG modes within an elliptical core
fiber than Laguerre Gaussian modes or Hermite Gaussian modes. Thus,
IG modes can be used as a program signal for spectroscopy in the
same manner that Laguerre Gaussian modes or Hermite Gaussian modes
are used. This enables the detection of types of materials and
concentration of materials using an IG mode probe signal.
[0383] The wave equation can be represented as a Helmholtz equation
in Cartesian coordinates as follows
(.gradient..sup.2+k.sup.2)E(x, y, z)=0
E(x, y, z) is complex field amplitude which can be expressed in
terms of its slowly varying envelope and fast varying part in
z-direction.
E(x, y, z)=.psi.(x, y, z)e.sup.jkz
[0384] A Paraxial Wave approximation may be determined by
substituting our assumption in the Helmholtz Equation.
( .gradient. 2 + k 2 ) .psi. j kz = 0 ##EQU00039## .delta. 2 .psi.
.delta. x 2 + .delta. 2 .psi. .delta. y 2 + .delta. 2 .psi. .delta.
z 2 - j 2 k .delta..psi. .delta. z = 0 ##EQU00039.2##
[0385] We then make our slowly varying envelope approximation
.delta. 2 .psi. .delta. x 2 << .delta. 2 .psi. .delta. y 2 ,
.delta. 2 .psi. .delta. z 2 , 2 k .delta..psi. .delta. z
##EQU00040## .gradient. t 2 .psi. + j 2 k .delta..psi. .delta. z =
0 ##EQU00040.2##
Which comprises a Paraxial wave equation.
[0386] The elliptical-cylindrical coordinate system may be define
as shown in FIG. 82.
x = acosh .xi.cos.eta. ##EQU00041## y = asinh .xi.sin
##EQU00041.2## .xi. .di-elect cons. ( 0 , .infin. ) , .eta.
.di-elect cons. ( 0 , 2 .pi. ) ##EQU00041.3## a = f ( z )
##EQU00041.4## where ##EQU00041.5## f ( z ) = f 0 w ( z ) w 0
##EQU00041.6##
[0387] Curves of constant value of trace confocal ellipses as shown
in FIG. 83.
x 2 a 2 cosh 2 .xi. + y 2 a 2 sinh 2 .xi. = 1 ( Ellipse )
##EQU00042##
[0388] A constant value of .eta. give confocal hyperbolas as shown
in FIG. 84.
x 2 a 2 cos 2 .eta. - y 2 a 2 sin 2 .eta. = 1 ( hyperbola )
##EQU00043##
[0389] An elliptical-cylindrical coordinate system may then be
defined in the following manner
.gradient. t 2 = 1 h .xi. 2 .delta. 2 .delta..xi. 2 + 1 h .eta. 2
.delta. 2 .delta..eta. 2 ##EQU00044##
Where h.sub..xi., h.sub..eta. are scale factors
h .xi. = ( .delta. x .delta..xi. ) 2 + ( .delta. y .delta..xi. ) 2
##EQU00045## h .eta. = ( .delta. x .delta..eta. ) 2 + ( .delta. y
.delta..eta. ) 2 ##EQU00045.2## h .xi. = h .eta. = a sinh 2 .xi. +
sin 2 .eta. ##EQU00045.3## .gradient. t 2 = 1 a 2 sinh 2 .xi.sin 2
.eta. ( .delta. 2 .delta..xi. 2 + .delta. 2 .delta..eta. 2 )
##EQU00045.4##
[0390] The solution to the paraxial wave equations may then be made
in elliptical coordinates. Paraxial Wave Equation in Elliptic
Cylindrical co-ordinates are defined as
1 a 2 ( sinh 2 .xi.sin 2 .eta. ) ( .delta. 2 .psi. .delta..xi. 2 +
.delta. 2 .psi. .delta..eta. 2 ) - j2k .delta..psi. .delta. z = 0
##EQU00046##
[0391] Assuming separable solution as modulated version of
fundamental Gaussian beam.
IG ( r .about. ) = E ( .xi. ) N ( .eta. ) exp ( j Z ( z ) ) .psi.
GB ( r .about. ) ##EQU00047## Where ##EQU00047.2## .psi. GB ( r
.about. ) = w 0 w ( z ) exp [ - r 2 w 2 ( z ) - j kr 2 2 R ( z ) -
j.psi. GS ( z ) ] ##EQU00047.3##
E, N & Z are real functions. They have the same wave-fronts as
.psi..sub.GB but different intensity distribution.
[0392] Separated differential equations are defined as
d 2 E d .xi. 2 - sinh2.xi. E .xi. - ( a - p cosh2.xi. ) E = 0
##EQU00048## d 2 N d .eta. 2 - sin2.eta. N .eta. - ( a - p
cos2.eta. ) = 0 - ( z 2 + z r 2 z r ) Z z = p ##EQU00048.2##
Where a and p are separation constants
= f 0 w 0 w ( z ) ##EQU00049##
[0393] The even solutions for the Ince-Gaussian equations are
IG pm e ( r .about. , ) = Cw o w ( z ) C p m ( j.xi. , ) C p m (
.eta. , ) exp ( - r 2 w 2 ( z ) ) .times. exp j ( kz + kr 2 2 R ( z
) - ( p + 1 ) .psi. GS ( z ) ) ##EQU00050##
The frequency of the even Ince Polynomials are illustrated in FIGS.
85A and 85B and the modes and their phases are illustrated in FIG.
86.
[0394] The odd solutions for the Ince-Gaussian equations are
IG pm o ( r .about. , ) = sw 0 w ( z ) S p m ( j.xi. , ) S p m (
.eta. , ) exp ( - r 2 w 2 ( z ) ) .times. exp j ( kz + kr 2 2 R ( z
) - ( p + 1 ) .psi. GS ( z ) ) ##EQU00051##
The frequency of the odd Ince Polynomials are illustrated in FIGS.
87A and 87B and the modes and their phases are illustrated in FIG.
88.
[0395] Thus, as previously discussed with respect to FIG. 59, by
combining two or more different types of spectroscopy techniques,
various types of different parameters may be monitored and used for
determining types and concentrations of sample materials. The use
of multiple types of spectroscopic parameter analysis enables for
more accurate and detailed analysis of sample types and
concentrations. Thus, any number of spectroscopic techniques such
as optical spectroscopy, infrared spectroscopy, Ramen spectroscopy,
spontaneous Ramen spectroscopy, simulated Ramen spectroscopy,
resonance Ramen spectroscopy, polarized Ramen spectroscopy, Ramen
spectroscopy with optical vortices, THz spectroscopy, terahertz
time domain spectroscopy, fluorescence spectroscopy, pump probe
spectroscopy, OAM spectroscopy, or Ince Gaussian spectroscopy may
be used in any number of various combinations in order to provide
better detection of sample types in concentrations. It should be
realized that the types of spectroscopy discussed herein are not
limiting in any combination of spectroscopic techniques may be
utilized in the analysis of sample materials.
Multi-Parameter Dual Comb Spectroscopy with OAM
[0396] One can perform precision spectroscopy with pairing optical
frequency combs which can improve the results. Referring now to
FIG. 89, in broadband frequency comb spectroscopy, the signal from
an optical frequency comb is read by a conventional spectrometer,
but in a technique called dual-comb spectroscopy, that conventional
spectrometer 8902 and the instrument's limitations on speed and
resolution are removed. Instead, a second frequency comb 8904 takes
on the work previously done by the spectrometer 8902. The result
can be dramatic gains in data acquisition speed, spectral
resolution and sensitivity. These techniques can be used in
conjunction with multi-parameter spectroscopy 8906 leveraging
wavelength, polarization and OAM spectroscopy 8908.
Optical Frequency Combs
[0397] An optical frequency comb 8904 is a spectrum consisting of
hundreds of thousands or millions of equally spaced, sharp
lines-analogous having a great many continuous-wave (CW) lasers
simultaneously emitting at different, equally spaced frequencies.
Optical combs can be generated in many ways; the most common method
uses a phase-stabilized, mode-locked ultrashort-pulse laser. In the
time domain. the laser produces a pulse train at a specific
repetition rate, and with a specific increasing additional
carrier-envelope phase with each successive pulse. When the
repetition rate and carrier-envelope phase of the pulse train are
both stabilized against radio- or optical-frequency references, a
Fourier transformation of the laser's periodic pulse train shows a
sharp, comb-like spectrum in the frequency domain.
[0398] If the frequency comb is well stabilized and referenced to
an absolute frequency standard, such as an atomic clock, the comb
spectrum becomes an extremely precise ruler for measuring optical
frequencies. That ruler has found applications in a wide variety of
scientific problems: high-resolution frequency measurements of
atomic, ionic or molecular transitions to answer fundamental
questions in physics; the detection of tiny amounts of Doppler
shift; and other applications in attosecond physics, ultrapure
microwave generation, time-frequency transfer over long distances,
manipulation of atomic qubits, and many others.
[0399] One of the most active research areas for frequency combs is
broadband molecular spectroscopy. The comb's millions of equally
spaced, sharp lines offer the opportunity to measure complex
broadband molecular signatures with high spectral resolution and
sensitivity. Exploiting those advantages, however, requires a
spectrometer of sufficiently high resolution to resolve each
individual comb line. One approach can be the use of a spectrometer
based on virtually imaged phased array (VIPA) disperser in
combination with a diffraction grating; another common scheme uses
an analytical chemistry, the Michelson-type Fourier transform
spectrometer, and replaces the conventional broadband, usually
incoherent light source with a frequency comb.
[0400] In this approach to frequency comb spmroscopy, the frequency
comb pulse train is split into interferometer arms, one of which
includes a mechanically scanned mirror, and the two pulse trains
are sent through the sample to be analyzed. As the mirror is
scanned, a series of interferograms is recorded with a sin
photo-receiver and a digitizer; Fourier transformation of the
interferograms generates the spectrum, with a resolution determined
by the maximum optical-path-length difference of the
interferometer.
The Dual-Comb Advantage
[0401] A key drawback of doing frequency comb spectroscopy with the
Michelson-type setup described is speed: the scan rate of the
setup, which is limited by the velocity of the scanning mirror, is
commonly only on the order of Hz. Dual-comb spectroscopy eases this
disadvantage by use: a second frequency comb, rather than a moving
mirror to supply the delay time. The result can be a significant
enhancement of the spectrometer's performance.
[0402] In the dual-comb setup, the pulse train forms a second comb,
with a slightly different pulse repetition rate from the first,
that is spatially combined with the train from the first comb. The
combined pulse train is passed through the sample to be analyzed,
and detected by a photo-receiver. The result, in the time domain,
is a repeated series of cross-correlation-like interferometric
signals between the pulses, with a steadily increasing time
difference based on the difference in repetition rate between the
two combs. The dual-comb interferograms thus have characteristics
similar to those of a conventional Michelson-type Fourier transform
spectrometer but because the dual-comb setup does not depend on the
mechanical motion of a mirror, its scanning rate is several orders
of magnitude faster than that of the Michelson-type
interferometer.
[0403] Another advantage of dual-comb spectroscopy emerges in the
frequency domain There, the mixing of the two optical combs, with
slightly different repetition rates, results in a third,
down-converted radio-frequency (RF) comb, with spacing between
teeth equivalent to the repetition rate difference between the two
optical combs. The sample's response is thus encoded on this
down-converted RF comb, and the beat measurement between the two
optical combs generates a multi-heterodyne signal that can be
recovered from the RF comb. In summary, the down-converted comb
inherits the coherence property of the optical frequency combs,
enabling broadband spectroscopy with a high resolution and accuracy
with the speed and digital signal processing advantages of RF
heterodyne detection.
Small Wearable Device
[0404] Compact wearable optical devices based on Raman and NIR
absorption to detect changes in physiological chemical levels in
the body may also be implemented. Along with the novel detection
scheme, we are also developing the compact integrated
electronic-photonic system (ultimately an integrated
silicon-photonic system). A wearable device 9000 should include the
following components as shown in FIG. 90. An MCU (microcontroller)
9002 controls overall operation of the wearable device 9000. BLE
(Bluetooth low energy) transmitter/receiver 9004 transmits signals
to and from the wearable device 9000. Trance-impedance amplifier
(TIA) for internally amplifying signals. Drivers 9008 for driving
LED/lasers within the device 9000. High resolution ADC 9010
performs analog to digital conversions. Flash memory 9012 stores
data within the wearable device 9000. Real-time clock 9014 controls
internal clocking operations.
[0405] The major requirement is low quiescent current for every
component, ability to enter deep sleep mode, low current
consumption in operating mode, low-frequency mode for real-time
clock/low power operation, and single battery operation of the MCU
(microcontroller) and BLE (blue-tooth low energy). MCU+BLE chipsets
of 2013-2015 model year provide the following component options:
[0406] a) EFM32 (MCU Silicon Laboratories)+CC2541 (BLE chip Texas
Instruments) or BCM20732 (Broadcom), or [0407] b) Single chip
solution form Nordic Semiconductors NRF51822 which includes similar
Cortex M0 core and BLE radio, BLE stack is realized via underling
Nordic proprietary OS (SoftDevice) which occupies about 100 kB of
chips memory.
[0408] Either of these two solutions is used in 90% of modern BLE
wearable devices. In the present case the preferred embodiment
would be using the single chip solution from Nordic Semiconductor.
Major characteristics are:
[0409] 1) External crystal for real-time clock,
[0410] 2) 256 kb of memory (256 kb-100 kb (SoftDevice)=156 kB for
the program and storage)
[0411] 3) Sleep mode in 1 uA range
[0412] 4) Support of all standard BLE profiles and adjustable radio
power up to 4 dBm.
It also supports ANT protocol which may be useful in future
development.
[0413] The near infrared laser diode system provides approximately
30 controllable channels between 1570 and 1600 nm, as well as an
additional tunable source between 1450 and 1600.
[0414] Similar portable devices may be used with respect to other
embodiments and uses described above, including the detection of
proteins and food spoilage or food organic bio-markers due to the
various biochemical mechanisms associated with food spoilage.
OAM Body-Imaging
[0415] Imaging through and parts of the body is critical for most
biomedical optical technology. Past work has developed imaging and
spectroscopy in select transmission windows in the NIR where
glucose and proteins have strong absorptions while water has
reduced absorption. Since optical detection of glucose or other
chemical compounds will most likely need to be in a region free of
strong absorptions from other molecules, and will take place with
OAM beams, imaging of the body tissues, brain, bone and skin with
OAM may be used. Possible routes to investigate would be phase
contrast and dark field imaging, ballistic transport of OAM through
scattering media in the NIR and birefringent imaging. The diode
lasers available for the wearable device can also be incorporated
into the NIR OAM imaging once a suitable detector is acquired and
tested. Single channel detectors in the NIR are cheaper than 2D CCD
arrays, however a scanning system and image construction software
would be needed when imaging with a single channel detector.
Potential Applications
[0416] A compact, handheld 3D spectrometer capable of simultaneous
polarization, wavelength, and OAM-spectroscopy operated in a broad
electromagnetic frequency range empowers consumers with tremendous
amounts of useful information about such things as their food and
air quality, household biological contaminants, medicinal
identification, and health-related issues such as real-time
information about dental caries. This section serves as an outline
of some of the potential applications of 3D spectroscopy.
Food Industry
[0417] Food substances primarily consist of water, fat, proteins,
and carbohydrates. The molecular structure and concentration of
food substances govern their functional properties. Quantification
of these properties dictates the quality of food in terms of
minimum standards of suitability for human consumption or exposure
which include chemical, biological, and microbial factors that may
impact such parameters as their shelf-life. Recent advances in
industrialization of our food supply chains and changes in consumer
eating habits have placed greater demand on the rapidity with which
our food must be analyzed for safety and quality. This demand
requires appropriate analytical tools such as spectroscopy.
[0418] Food spectroscopy is a desirable analysis method because it
requires minimal or no sample preparation as well rapid,
production-line measurements. Given the nature of spectroscopic
analysis, multiple tests may be done on the sample.
[0419] Outside the industrialized production line of our food
supply, novel spectroscopic techniques could be employed at the
level of individual consumers. For example, an individual consumer
may spectroscopically measure the sugar concentration in his foods,
overall food quality, ripeness, or identify a watermelon in the
local grocery store as having been spoiled using a pocket size
laser-based spectrometer.
Nanoscale Material Development for Defense and National
Security
[0420] Nanoscale material development for defense and national
security technologies generally necessitates the binding site to
recognize the target of interest. Several spectroscopic techniques
are currently based on absorption, scattering, of light, such as
electron absorption (UV-vis), photoluminescence (PL), infrared (IR)
absorption, and Raman scattering while more advanced techniques
include single molecule spectroscopy, sum frequency generation, and
luminescence up-conversion. These spectroscopy technologies aid in
the fabrication process of nanoscale material architectures
employed as biological and chemical sensors.
Chemical Industry
[0421] Optical spectroscopy of gas sensors is useful for a variety
of environmental, industrial, medical, scientific and household
applications. The gas may be hazardous to human health, an
atmospheric pollutant, or important in terms of its concentration
for industrial or medical purposes. Aside from triggering an alarm,
it is frequently desirable to measure accurate, real-time
concentrations of a particular target gas, which is often in a
mixture of other gases. Consumers may use household units to
monitor air for biological or chemical hazards such as airborne
germs or carbon monoxide as well as surfactant contaminations on
and around children's play areas, toys, and bedrooms. Such units
would be useful in school classrooms, business offices, and
shopping malls to alert to facilities managers to potential health
hazards. Further units may be useful in various industrial
settings, including for example, chemical and/or petrochemical
facilities, including but not limited to, using near-infrared
spectroscopy. In addition to improved environmental benefits of
detecting various fugitive emissions of gases, such detection
presents various economic benefits for industrial operators to fix
fugitive emission sources for increases in product recovery and
abatement of governmental fines.
Pharmaceutical Industry
[0422] The manufacturing process of highly precise drug
concentrations in pills, capsules and liquids requires strict
real-time monitoring as may be performed by optical spectroscopy
technologies. Once produced and distributed, consumers may readily
identify pills and medication at home using an advanced, real-time
spectroscopy technique integrated into a handheld device.
Medical Industry
[0423] There is strong interest in developing more sophisticated
optical biopsy technologies that non-invasively detect disease.
These technologies may be driven by spectroscopy that may optically
biopsy tissues without the need to remove it from the patient's
body. Such a technology may be developed to produce a photonics
finger imager for accurate prostate checkups, breast mammograms,
and other cancer-detection procedures. A pocket-sized
dermatological spectrometer would give patients private, real-time
information that may be combined with the patient's medical record
for discussion with medical professionals.
[0424] The use of small, handheld optical spectrometers can be
integrated into a patient's routine health maintenance schedule. An
example is the early detection of chemicals associated with
Alzheimer's disease and Parkinson's by spectroscopic detection
during routine eye exams.
Dentistry
[0425] Everyday personal dental care requires small tools and
instruments such as toothbrushes and dental floss. A
toothbrush-size optical spectrometer would be useful to detect the
onset of small dental caries (tooth decay and cavities) and alert
the consumer to schedule a visit to the family dentist who may have
been sent tooth-specific information before the scheduled
visit.
Biomedical Photonics
[0426] These technologies can be applied to, and not limited to,
neuro-imaging applications such as optical spectroscopy and
correlation methods to measure oxygen and blood flow; the
development of new microscopes for functional imaging to improve
the quantitative interpretation of measurement of brain activities
and psychology using functional near-infrared spectroscopy; the
development technologies such as diffuse correlation spectroscopy
to measure blood flow; and the development of multi-spectral
optical imaging of cerebral hemoglobin.
[0427] It will be appreciated by those skilled in the art having
the benefit of this disclosure that this system and method for the
detection of the presence of materials within a sample based on a
unique signature. It should be understood that the drawings and
detailed description herein are to be regarded in an illustrative
rather than a restrictive manner, and are not intended to be
limiting to the particular forms and examples disclosed. On the
contrary, included are any further modifications, changes,
rearrangements, substitutions, alternatives, design choices, and
embodiments apparent to those of ordinary skill in the art, without
departing from the spirit and scope hereof, as defined by the
following claims. Thus, it is intended that the following claims be
interpreted to embrace all such further modifications, changes,
rearrangements, substitutions, alternatives, design choices, and
embodiments.
* * * * *
References