U.S. patent application number 12/697083 was filed with the patent office on 2011-08-04 for broadband optics for manipulating light beams and images.
This patent application is currently assigned to Beam Engineering for Advanced Measurement Co.. Invention is credited to Brian Kimball, Sarik Nersisyan, Diane Steeves, Nelson Tabirian.
Application Number | 20110188120 12/697083 |
Document ID | / |
Family ID | 44341449 |
Filed Date | 2011-08-04 |
United States Patent
Application |
20110188120 |
Kind Code |
A1 |
Tabirian; Nelson ; et
al. |
August 4, 2011 |
BROADBAND OPTICS FOR MANIPULATING LIGHT BEAMS AND IMAGES
Abstract
The objective of the present invention is providing optical
systems for controlling with propagation of light beams in lateral
and angular space, and through optical apertures. Said light beams
include laser beams as well as beams with wide spectrum of
wavelengths and large divergence angles. Said optical systems are
based on combination of diffractive waveplates with diffractive
properties that can be controlled with the aid of external stimuli
such as electrical fields, temperature, optical beams and
mechanical means.
Inventors: |
Tabirian; Nelson; (Winter
Park, FL) ; Nersisyan; Sarik; (Orlando, FL) ;
Kimball; Brian; (Shrewsbury, MA) ; Steeves;
Diane; (Franklin, MA) |
Assignee: |
Beam Engineering for Advanced
Measurement Co.
Winter Park
FL
|
Family ID: |
44341449 |
Appl. No.: |
12/697083 |
Filed: |
January 29, 2010 |
Current U.S.
Class: |
359/573 |
Current CPC
Class: |
G02B 5/1866 20130101;
G02B 5/1828 20130101; G02B 27/4272 20130101; G02B 27/44
20130101 |
Class at
Publication: |
359/573 |
International
Class: |
G02B 27/44 20060101
G02B027/44 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with Government support under
Contract No. W911QY-07-C-0032.
Claims
1. A system for positioning light beams comprising: (a) a light
source; (b) a plurality of diffractive waveplates; (c) means for
independently controlling the diffractive properties of individual
diffractive waveplates.
2. The system of claim 1 wherein the light source includes means
for shaping the light beam it irradiates by controlling one or a
combination of its characteristics: divergence, spectral content,
polarization, profile.
3. The system of claim 1 wherein the plurality of diffractive
waveplates comprises at least one pair of optically identical
diffractive waveplates.
4. The system as in claim 1 wherein the material properties of at
least one in the plurality of diffractive waveplates, including
optical anisotropy, optical axis orientation, and layer thickness,
can be controlled with one or a combination of the following
stimuli: electric field, magnetic field, optical radiation,
temperature, mechanical stress.
5. The system of claim 4 wherein the plurality of diffractive
waveplates is deposited sequentially on the same substrate.
6. The system of claim 1 wherein the means for independently
controlling the diffractive properties of individual diffractive
waveplates include one or the combination of the following:
electric field, magnetic field, optical radiation, temperature,
mechanical rotation assembly, mechanical displacement assembly.
7. The system of claim 1 wherein the light beam is produced by a
laser source with quasi-monochromatic spectrum.
8. The system of claim 1 wherein the light beam is produced by a
source with broadband angular spectrum.
9. The system of claim 1 wherein the diffractive waveplates deflect
light with nearly 100% efficiency in a broad spectrum of
wavelengths.
10. The system of claim 7 wherein the light beam is produced by a
source with broadband wavelength spectrum.
11. The system of claim 1 further comprising an optical setup for
receiving and controlling the light at the output of the plurality
of diffractive waveplates, said optical setup including one or a
combination of the following: spatial filters, spectral filters,
polarizers, diffraction gratings.
Description
CROSS REFERENCES
[0002] [1] S. R. Nersisyan, N. V. Tabiryan, D. M. Steeves, B. R.
Kimball, "Optical Axis Gratings in Liquid Crystals and their use
for Polarization insensitive optical switching," J. Nonlinear Opt.
Phys. & Mat., 18, 1-47 (2009).
[0003] [2] P. F. McManamon, P. J. Bos, M. J. Escuti, J. Heikenfeld,
S. Serati, H. Xie, E. A. Watson, A Review of Phased Array Steering
for Narrow-Band Electrooptical Systems, Proceedings of the IEEE,
97, pp. 1078-1096, 2009.
[0004] [3] S. R. Nersisyan, N. V. Tabiryan, L. Hoke, D. M. Steeves,
B. Kimball, Polarization insensitive imaging through polarization
gratings, Optics Express, 17 (3), 1817-1830, 2009.
[0005] [4] C. Oh, J. Kim, J. F. Muth, M. Escuti, A new beam
steering concept: Riesley gratings, Proc. SPIE, vol. 7466, pp.
74660J1-J8, 2009.
[0006] [5] J. C. Wyant, Rotating diffraction grating laser beam
scanner, Applied Optics, 14, 1057-1058, 1975.
TABLE-US-00001 U.S. Patent Documents 7,319,566 January 2008 Prince
et al. 7,324,286 January 2008 Glebov et al. 6,792,028 September
2004 Cook et al. 3,721,486 March 1973 Bramley
RIGHTS OF THE GOVERNMENT
[0007] The invention described herein may be manufactured and used
by or for the Government of the United States for all governmental
purposes without the payment of any royalty.
FIELD OF THE INVENTION
[0008] This invention relates to optical beam control and, in
particular, to methods, systems, apparatus and devices for
manipulating with light beams, including laser beams and beams with
wide spectra and divergence angles, by translating them in the
lateral direction and varying their propagation direction over
large angles for optical switching, beam scanning, spectral
modulation, optical tweezers, thermal seeker, imaging, information
displays, and other photonics applications.
BACKGROUND OF THE INVENTION
[0009] The present invention relates to optical systems for
controlling with propagation of light beams. Pointing and
positioning systems are enabling components for most laser
applications. Conventionally, this is accomplished using mirrors,
scan wheels, optical wedges, and other two-axis gimbal arrangements
as exemplified, for example, in the U.S. Pat. No. 7,319,566 to
Prince et al. These opto-mechanical systems are complex, bulky and
heavy for large area beams. For example, the prism apex angle,
hence its thickness is increased to achieve larger deflection
angles. The electromechanical systems for rotation, translation or
oscillation of such mirrors, prisms, and other optical components
require high electrical power for their operation. They are
relatively slow and have limited range of angles that could be
covered within given time period.
[0010] Thus, there is a need for thin, light-weight, fast, and
inexpensive pointing, positioning, and switching systems for light
beams, particularly, for laser beams. The state-of-the-art
developments include all-electronics systems and rotating
diffraction gratings. The all-electronics systems with no moving
parts, as reviewed in P. F. McManamon, P. J. Bos, M. J. Escuti, J.
Heikenfeld, S. Serati, H. Xie, E. A. Watson, A Review of Phased
Array Steering for Narrow-Band Electrooptical Systems, Proceedings
of the IEEE, Vol. 97, pages 1078-1096 (2009), require a large
number of high efficiency diffraction gratings and spatial light
modulators and/or electrically controlled waveplates. As a result,
the overall transmission of these systems is reduced along with
their radiation damage threshold, and their speed is limited by the
liquid crystal spatial light modulators and variable retarders.
[0011] Rotating diffraction gratings as described in J. C. Wyant,
"Rotating diffraction grating laser beam scanner," Applied Optics,
14, pages 1057-1058 (1975), and in the U.S. Pat. No. 3,721,486 to
Bramley, partially solves the problem of obtaining larger
diffraction angle in thinner optical system, compared, for example
to the system of Risley prisms. The light beam diffracted by the
first grating in the path of the beam is further diffracted by the
second grating. Depending on orientation of those gratings with
respect to each other, the deflection angle of the beam can thus be
varied between nearly 0 to double of the diffraction angle
exhibited by a single grating. The problem with such systems is
that phase gratings typically diffract light into multiple orders
that need to be blocked along with the order beam. High efficiency
Bragg type gratings have narrow spectral and angular range as
described in the U.S. Pat. No. 7,324,286 to Glebov et al., and can
be used practically for laser beams only, expanded and collimated
to minimize divergence. Blazed gratings such as proposed in the
U.S. Pat. No. 6,792,028 to Cook et al., still exhibit a multitude
of diffraction orders due to their discontinuous structure and do
not improve considerably on angular selectivity and efficiency.
[0012] The cycloidal diffractive waveplates (DWs), essentially,
anisotropic plates meeting half-wave condition but with optical
axis orientation rotating in the plane of the waveplate in a
cycloidal manner, as described in the review S. R. Nersisyan, N. V.
Tabiryan, D. M. Steeves, B. R. Kimball, "Optical Axis Gratings in
Liquid Crystals and their use for Polarization insensitive optical
switching," J. Nonlinear Opt. Phys. & Mat., 18, 1-47 (2009), do
not have the disadvantages of conventional phase gratings.
Moreover, DWs, referred to also as optical axis gratings and
polarization gratings, can provide nearly 100% diffraction
efficiency in micrometer thin layers. Furthermore, due to their
waveplate nature, their diffraction spectrum is broadband, and can
even be made practically achromatic. Due to their thinness and high
transparency, they can be used in high power laser systems.
[0013] Thus, replacing Risley prisms, wedges, mirrors and/or phase
gratings with DWs, provides many advantages for manipulating with
light beams and imaging. As shown in S. R. Nersisyan, N. V.
Tabiryan, L. Hoke, D. M. Steeves, B. Kimball, Polarization
insensitive imaging through polarization gratings, Optics Express,
17, 1817-1830 (2009), not only laser beams, but complex images can
be steered over large angles without light attenuation or image
deformation. That paper further showed that utilizing a pair of
closely spaced DWs, one of them with switchable characteristics, it
is possible to manipulate with transmission of unpolarized beams
and images. This concept suggested and demonstrated in S. R.
Nersisyan, N. V. Tabiryan, L. Hoke, D. M. Steeves, B. Kimball,
"Polarization insensitive imaging through polarization gratings,"
Optics Express, 17, 1817-1830 (2009) was subsequently cited and
tested in C. Oh, J. Kim, J. F. Muth, M. Escuti, "A new beam
steering concept: Riesley gratings," Proc. SPIE, vol. 7466, pp.
74660J1-J8 (2009).
BRIEF SUMMARY OF THE INVENTION
[0014] Thus, the objective of the present invention is providing
means for switching and manipulating with light beams and images in
lateral and angular space using a set of DWs capable of deflecting
nearly 100% of light using thin material layers for a broad band of
wavelengths and divergence angles.
[0015] The second objective of the present invention is
incorporating in said set DWs with controlled characteristics of
their optical properties for further enhancing optical manipulation
capabilities of said systems.
[0016] A further objective of the present invention is providing
optical systems, incorporating said DW set, wherein manipulation of
light and images with the DW set is transformed into transmission
modulation of at the output of the optical system.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] FIG. 1A schematically shows deflection of a circularly
polarized light beam with a pair of diffractive waveplates.
[0018] FIG. 1B schematically shows the structure of diffractive
waveplates at different rotational positions.
[0019] FIG. 2A shows sample dependence of the propagation angle of
a light beam at the output of a pair of diffractive waveplates as a
function of the rotational position between the waveplates.
[0020] FIG. 2B demonstrates the capability of a pair of diffractive
waveplates to steer with no distortions complex images carried by
an unpolarized light.
[0021] FIG. 3A schematically shows the displacement of a light beam
by a pair of diffractive waveplates with parallel orientation of
their optical axis modulation directions.
[0022] FIG. 3B schematically shows the increase in the resultant
deflection angle of a light beam by a pair of diffractive
waveplates with anti-parallel orientation of their optical axis
modulation directions.
[0023] FIG. 3C shows the optical axis orientation pattern in
diffractive waveplates with anti-parallel orientation of their
optical axis modulation directions.
[0024] FIG. 4A schematically shows increasing of the deflection
angle of a light beam by a set of four diffractive waveplates each
arranged anti-parallel with respect to the previous one.
[0025] FIG. 4B demonstrates increasing deflection angle of a light
beam by increasing the number of diffractive waveplates from one to
four, and comparing them to the original propagation direction of
the beam.
[0026] FIG. 5 shows increasing deflection angle of a light beam by
a system of diffractive waveplates tilted with respect to each
other.
[0027] FIGS. 6A and B schematically show switching between
transmittive and deflective states of a pair of diffractive
waveplates when switching one of the diffractive waveplates into an
optically homogeneous non-diffractive state shown in C.
[0028] FIG. 7 shows a schematic of a beam combining function of a
pair of diffractive waveplates.
[0029] FIGS. 8A, B and C show a schematic of a system for
controlling the spectrum of a light beam with the aid of a set of
diffractive waveplates.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Before explaining the disclosed embodiment of the present
invention in detail it is to be understood that the invention is
not limited in its application to the details of the particular
arrangement shown since the invention is capable of other
embodiments. Also, the terminology used herein is for the purpose
of description and not limitation.
[0031] The preferred embodiment of the present invention includes
two DWs, marked with numerals 103 and 105 in FIG. 1A, arranged
parallel to each other in close proximity. At the output of the
system of DWs 103 and 105, the pointing direction of the light beam
108, circularly polarized as shown by spirals 102 and 107, is, in
general, different from that of the propagation direction of the
light beam 101 incident on the system, controlled with relative
rotational positions of the DWs as schematically shown by arrows
104 and 106. The optical axis orientation pattern corresponding to
different rotational positions of said DWs is shown in FIG. 1B
wherein the axes of elongated ellipses 109 correspond to local
optical axis orientation direction. In the preferred embodiment,
DWs are made of liquid crystal polymers though other optically
anisotropic materials and material structures such as subwavelength
gratings can be used as well. In general, the layer of DW,
typically only a few micrometer thick, is coated on a substrate 110
for stability and robustness. The substrate can be made of a
material adequate for the particular application. As an example, a
fused silica can be used when controlling UV light beams, and
highly transparent glass materials with low absorption can be used
for controlling high power laser beams.
[0032] The plot of output angles measured for a sample system as a
function of angular position between the DWs in S. R. Nersisyan, N.
V. Tabiryan, L. Hoke, D. M. Steeves, B. Kimball, "Polarization
insensitive imaging through polarization gratings," Optics Express,
17 (3), 1817-1830 (2009) is shown in FIG. 2A for normal incidence
of the beam on the first DW. In the setup shown in FIG. 1A, the
polarization of the incident beam is assumed circular, as
schematically shown by the spiral 102. The output beam 108 in this
case maintains the circular polarization state 107. In case of
incident unpolarized or linearly polarized beam, two beams of
orthogonal circular polarization are generated at the output of the
system of two DWs, and the angle between them changes from nearly 0
to nearly double of the diffraction angle depending on relative
rotational positions between the DWs as shown in FIG. 2B for light
beam carrying a complex image. No image distortions occurs in this
process.
[0033] Increasing the distance .DELTA.z between two identical DWs
302 and 304, FIG. 3, introduces transverse shift .DELTA.x of the
beam 305 emerging from the system with respect to the position of
the input beam 301 as a result of deflection of the beam by the
first DW 302. Said emerging beam 305 propagates parallel to the
input beam 301 in case the optical axis modulation directions of
DWs 302 and 304 are parallel, FIG. 3A, and it also changes in
propagation direction when the DW 304 is rotated with respect to DW
302 into a new position 306, FIG. 3B. The overall deflection angle
of the beam can be maximized positioning the output DW 306
anti-parallel with respect to the input DW 302. The optical axis
alignment patterns for anti-parallel DWs 302 and 306 are
schematically shown in FIG. 3C. The beam can be steered over
arbitrarily large angles by adding DWs into the system. Four DWs,
406-409, are shown in FIG. 4A as an example. The input light 401
undergoes four deflections, 402-405. In order for each subsequent
deflection to further increase the resultant deflection angle, the
DWs 407 and 409 have to be arranged anti-parallel to DWs 406 and
408. A demonstration of light deflection by such a system of four
DWs is shown in FIG. 4B. In general, DWs can be tilted with respect
to each other such as each of the subsequent DWs is nearly
perpendicular to the beam deflected by the previous DW. The DWs 507
and 509 are anti-parallel to the DWs 506 and 508, and all four
deflected beam 502-505 of the input beam 501 result in increasing
total deflection angle.
[0034] In another embodiment, one or more DWs in a system can be
switched between diffractive and non-diffractive states, optically,
thermally, electrically, mechanically, or by any other means, due
the effect of external stimuli on optical anisotropy and optical
axis orientation modulation pattern. For example, the DW can be
made of azobenzene liquid crystal polymer that can be transformed
into isotropic state or realigned by light beams as discussed in S.
R. Nersisyan, N. V. Tabiryan, D. M. Steeves, B. R. Kimball,
"Optical Axis Gratings in Liquid Crystals and their use for
Polarization insensitive optical switching," J. Nonlinear Opt.
Phys. & Mat., 18, 1-47 (2009). Alternatively, DWs can be
transformed into homogeneous orientation state by electrical fields
if they are made of liquid crystals or liquid crystal polymer
network materials.
[0035] Particularly important is the case shown in FIG. 6 when a DW
603 with a fixed diffractive property is paired with a controllable
DW 602 in configuration when their optical axis modulation
directions are parallel. As noted in S. R. Nersisyan, N. V.
Tabiryan, L. Hoke, D. M. Steeves, B. Kimball, "Polarization
insensitive imaging through polarization gratings," Optics Express,
17 (3), 1817-1830 (2009), this state corresponds to total
cancellation of diffraction, and such a pair allows transmitting
the light beam 601 through the system as shown schematically in
FIG. 6A. An image sensor 604 furnished with an aperture 605 large
enough not to block the transmitted beam would not register any
distortions to the beam. In case the DW 602 is transformed into a
non-diffractive state 606, the diffraction of, generally, an
unpolarized light on the remaining DW 603 redirects the input beam
601 into diffracted beams 607 and 608 as shown in FIG. 6B,
diffracting it into orthogonal circular polarized components in
case of unpolarized or linearly polarized incident beam. No beam is
acting on an image sensor 604 in this case provided the deflected
beams propagate beyond the receiving aperture of the image sensor.
Thus, the system described in FIG. 6 undergoes switching from high
transmission to no or low-transmission state as a result of
switching the structure of one of the DWs in the system from
diffractive state 603 into a non-diffractive state 606, FIG. 6C.
Indeed, such change in transmission through particular aperture can
be obtained also by mechanically changing the rotational position
of the DWs or the distance between them.
[0036] Paired DWs and their systems can have many applications in
photonics. A setup for beam combining is shown in FIG. 7. Two
parallel propagating light beams of orthogonal circular
polarizations 701 and 704, after being deflected by the first DW
707 are further deflected into beams 702 and 705, emerging as
overlapping beams of the same propagation direction 703 and 706 by
the second DW 707 in FIG. 7.
[0037] Given the thinness of individual DW layers, a multilayer
system can be designed for spectrally selective switching without
compromising the high throughput and the small size of the system.
In the embodiment shown in FIG. 8, a set of DW pairs is used for
controlling with the spectral content of the transmitted light by
allowing light at different portions of the spectrum at least
partially be deflected out of the system. The beams 801 and 804 in
FIG. 8 are assumed to possess with different, non-overlapping,
spectral content. The individual DWs in the first pair 807 are
optimized for diffracting the light beam 801 while having
diffraction spectrum out of the spectral range of the beam 804. The
individual DWs in the second pair 808 are optimized for diffracting
the light beam 804 while having diffraction spectrum out of the
spectral range of the beam 801. Thus, when DWs in both pairs are
parallel aligned with respect to their optical axis modulation
direction, all the light is transmitted, and the spectral content
of the output light is the same as in the input light. In this case
shown in FIG. 8A, the input light 801 propagates through the first
DW pair into the beam 802 without changing its propagation
direction due to diffraction on both DWs constituting the pair 807.
The beam 802 further propagates through the second DW pair 808 into
the beam 803 without deflection since its spectrum is out of the
diffraction spectrum of the second DW pair 808. Similarly, the
input light 804 propagates through the first DW pair into the beam
805 without changing its propagation direction since its spectrum
is out of the diffraction spectrum of the first DW pair 807. The
beam 805 further propagates through the second DW pair 808 into the
beam 806 due to the diffraction on both DWs constituting the pair
808.
[0038] In case one of the DWs constituting the first pair 807 is
switched into non-diffractive state 809, or is rotated to double
the diffraction angle of the beam 801 by the first DW in the pair
807, the beam 801 is diffracted out of the optical system into a
beam 810. Propagation of the beam 804 is not affected by that. Thus
the light spectrum obtained at the output of the optical system
coincides with that of the beam 804, FIG. 8B.
[0039] In case one of the DWs constituting the second pair 808 is
switched into non-diffractive state 811, or is rotated to double
the diffraction angle of the beam 805 by the first DW in the pair
808, the beam 805 is diffracted out of the optical system into a
beam 812. Propagation of the beam 802 is not affected by that. Thus
the light spectrum obtained at the output of the optical system
coincides with that of the beam 801, FIG. 8C.
[0040] Although the present invention has been described above by
way of a preferred embodiment, this embodiment can be modified at
will, within the scope of the appended claims, without departing
from the spirit and nature of the subject invention.
* * * * *