U.S. patent application number 15/004575 was filed with the patent office on 2017-07-27 for device, method, and system for imaging laser amplifier.
The applicant listed for this patent is Advanced Systems & Technologies, Inc.. Invention is credited to Anatoliy Khizhnyak, Vladimir Markov.
Application Number | 20170214211 15/004575 |
Document ID | / |
Family ID | 59350401 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170214211 |
Kind Code |
A1 |
Markov; Vladimir ; et
al. |
July 27, 2017 |
DEVICE, METHOD, AND SYSTEM FOR IMAGING LASER AMPLIFIER
Abstract
An optical image amplifier device capable of amplifying
low-intensity backscattered illumination includes an optical port
having an input, an output, and a controller having an ON state and
an OFF state, the controller connecting the input and the output to
form an optical loop in the ON state and disconnecting the input
and the output in the OFF state, and an optical relay housing the
optical loop and connected to the optical port having a gain medium
configured for amplifying a signal beam propagating inside the
optical loop in the ON state.
Inventors: |
Markov; Vladimir; (Irvine,
CA) ; Khizhnyak; Anatoliy; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Advanced Systems & Technologies, Inc. |
Irvine |
CA |
US |
|
|
Family ID: |
59350401 |
Appl. No.: |
15/004575 |
Filed: |
January 22, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 17/89 20130101;
G01S 17/66 20130101; H01S 3/10076 20130101; H01S 3/10061 20130101;
H01S 3/083 20130101; H01S 3/106 20130101; H01S 3/1003 20130101;
H01S 3/235 20130101 |
International
Class: |
H01S 3/10 20060101
H01S003/10; G01S 17/66 20060101 G01S017/66; G01S 17/89 20060101
G01S017/89; H01S 3/106 20060101 H01S003/106 |
Goverment Interests
STATEMENT REGARDING GOVERNMENT RIGHTS
[0001] This invention was made with Government support under
Contract No. FA9453-13-C-0118 awarded by the United States Air
Force. The Government has certain rights in this invention.
Claims
1. An optical image amplifier device, comprising: an optical relay
housing an optical loop and having a gain medium; and an optical
port connected to the optical relay and having an input that
includes input optics for inputting a signal beam into the optical
relay, an output that includes output optics for outputting the
signal beam after being amplified, and a controller having an ON
state and an OFF state, the controller connecting the input and the
output to form the optical loop in the ON state and disconnecting
the input and the output in the OFF state, the gain medium being
configured to amplify the signal beam propagating inside the
optical loop when the controller is in the ON state.
2. The amplifier device of claim 1 wherein the controller is
positioned between a first polarizer and a second polarizer, the
controller further comprising: a half-wave plate and an
electronically controlled wave plate.
3. (canceled)
4. The amplifier device of claim 1 wherein the optical relay
further comprises a plurality of image formation optics.
5. The amplifier device of claim 2 wherein the first polarizer is
positioned adjacent to a first side of the electronically
controlled wave plate and configured to reflect the signal beam
when the electronically controlled wave plate is in the ON
state.
6. The amplifier device of claim 5 wherein the second polarizer is
positioned adjacent to a second side of the electronically
controlled wave plate and configured to reflect the signal beam
when the electronically controlled wave plate is in the ON
state.
7. The amplifier device of claim 6 wherein the optical relay
includes a first mirror positioned adjacent to a first side of the
gain medium and at an angle relative to the second polarizer and
configured to reflect the signal beam from the second polarizer to
the gain medium.
8. The amplifier device of claim 7 wherein the optical relay
includes a second mirror positioned adjacent to a second side of
the gain medium and positioned at an angle relative to the first
polarizer and configured to reflect the amplified signal beam
received from the gain medium to the first polarizer.
9. (canceled)
10. A method of amplifying an intensity of a light beam,
comprising: inputting the light beam into an input of an optical
port that has input imaging optics when a controller is set in an
OFF state; switching the controller to an ON state to create an
optical loop within the optical port and an optical relay to trap
the light beam; amplifying the light beam through successive passes
through the optical loop; switching the controller to the OFF state
to allow the amplified light beam to be output; and outputting the
amplified light beam through an output of the optical port that has
output imaging optics.
11. The method of claim 10 further comprising, after inputting the
light beam into the input, propagating the light beam through an
optical relay to fill the optical relay with the light beam.
12. The method of claim 11 further comprising, after propagating
the light beam, outputting the light beam through the output of the
optical port.
13. (canceled)
14. The method of claim 10 wherein the optical relay comprises a
plurality of image formation optics.
15. (canceled)
16. A system for amplifying a signal beam comprising: an amplifier
device, comprising: an optical port having an input, an output, and
a controller having an ON state and an OFF state, the controller
connecting the input and the output to form an optical loop in the
ON state and disconnecting the input and the output in the OFF
state; and an optical relay housing the optical loop and connected
to the optical port having a gain medium configured for amplifying
the signal beam propagating inside the optical loop in the ON
state; a processor for processing the amplified signal beam to
generate an image; and a display for displaying the generated
image.
17. The system of claim 16 wherein the controller comprises an
electronically controlled wave plate having an ON state and an OFF
state.
18. The system of claim 17 wherein the amplifier device further
comprises: a first polarizer positioned adjacent to a first side of
the electronically controlled wave plate and configured to reflect
the signal beam when the electronically controlled wave plate is in
the ON state; and a second polarizer positioned adjacent to a
second side of the electronically controlled wave plate and
configured to reflect the signal beam when the electronically
controlled wave plate is in the ON state.
19. The system of claim 18 wherein the amplifier device further
comprises: a gain medium configured for receiving the signal beam
and amplifying the signal beam to produce an amplified signal beam;
a first mirror positioned adjacent to a first side of the gain
medium and at an angle relative to the second polarizer and
configured to reflect the signal beam from the second polarizer to
the gain medium; and a second mirror positioned adjacent to a
second side of the gain medium and positioned at an angle relative
to the first polarizer and configured to reflect the amplified
signal beam received from the gain medium to the first
polarizer.
20. The system of claim 19 wherein the amplifier device further
comprises: a first imaging lens positioned between the second
polarizer and the first mirror; and a second imaging lens
positioned between the first polarizer and the second mirror.
Description
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to optics and more
particularly, to coherent optical amplifiers of a light field
scattered by an object that is not just a signal beam, and can be
used to perform surveillance, and active or passive tracking of the
object.
[0004] 2. Description of the Related Art
[0005] Active laser surveillance (ALS) can be used for tracking and
comprehensive characterization of distant objects. For example, ALS
can be used for active and passive space surveillance for
pinpointing relatively small but still potentially devastating
meteorites, comets, and debris that threaten to strike terrestrial
or manmade space objects, such as a spacecraft. Early detection of
these objects would provide an advanced alert to allow time for
safety actions, such as evacuation of threatened areas on the
ground or change of orbital parameters in the case of spacecraft.
However, considering the distances involved, active detection and
imaging of such remote objects remains a task that is very
difficult to fully achieve due to the low level of intensity of
backscattered light signals. Attempts to amplify the backscattered
light by using currently available methods result in amplification
of the noise associated with the signal, and so is of limited
use.
[0006] Similar issues arise regarding imaging and surveillance of
ground facilities or objects of interest, such as state borders,
military bases, ports, bridges, reservoirs, and in the private
sector, such as sports arenas, airports, malls, industrial
buildings, and other large public buildings. For example, when used
for a covert surveillance mission, low-level illumination intensity
is preferred to reduce the probability of its detection from the
object under surveillance. However, this low-level illumination
intensity results in a low-intensity backscattered light field
which makes it harder to detect by the surveillance module. Other
scenarios that require low-intensity coherent imaging include
behavioral studies of live species and microorganisms that often do
not tolerate a high-intensity illumination.
[0007] Accordingly, there is a need for a system and method of
amplifying a laser signal that overcomes the shortcomings stated
above.
SUMMARY OF THE INVENTION
[0008] The contents of this summary section are provided only as a
simplified introduction to the invention, and are not intended to
be used to limit the scope of the appended claims. The present
disclosure has been described above in terms of presently preferred
embodiments so that an understanding of the present disclosure can
be conveyed. However, there are other embodiments not specifically
described herein for which the present disclosure is applicable.
Therefore, the present disclosure should not be seen as limited to
the forms shown, which should be considered illustrative rather
than restrictive.
[0009] The present invention aims to address the above-cited
limitations in the current state-of-the-art ALS by providing the
ability to amplify a low-intensity backscattered light field by
successively amplifying the light field through an optical loop
also referred to herein as an optical cavity. Further in this
invention we refer to this object scattered light that carries
information on the object, including its imagery data, as a signal
beam. A signal beam is received at an input of the amplifier device
and is allowed to propagate through an optical relay containing a
gain medium. A controller is toggled into an ON state to trap the
signal beam within the optical relay so that the signal beam
follows an optical loop to become amplified through successive
passes through the gain medium. After a desired level of
amplification of the signal beam is achieved, the controller is
toggled into an OFF state and an amplified signal beam is outputted
from the amplifier.
[0010] An exemplary embodiment of the present invention's optical
image amplifier device capable of amplifying low-intensity
backscattered illumination comprises an optical port having an
input, an output, and a controller having an ON state and an OFF
state, the controller connecting the input and the output to form
an optical loop in the ON state and disconnecting the input and the
output in the OFF state, and an optical relay housing the optical
loop and connected to the optical port having a gain medium
configured for amplifying a signal beam propagating inside the
optical loop in the ON state.
[0011] In related versions, the controller is positioned between a
first polarizer and a second polarizer, the controller further
comprising a half-wave plate and an electronically controlled wave
plate.
[0012] In related versions, the input comprises input optics for
inputting the signal beam into the optical relay.
[0013] In related versions, the optical relay further comprises a
plurality of image formation optics.
[0014] In related versions, the first polarizer is positioned
adjacent to a first side of the electronically controlled wave
plate and configured to reflect the signal beam when the
electronically controlled wave plate is in the ON state.
[0015] In related versions, the second polarizer is positioned
adjacent to a second side of the electronically controlled wave
plate and configured to reflect the signal beam when the
electronically controlled wave plate is in the ON state.
[0016] In related versions, the optical relay includes a first
mirror positioned adjacent to a first side of the gain medium and
at an angle relative to the second polarizer and configured to
reflect the signal beam from the second polarizer to the gain
medium.
[0017] In related versions, the optical relay includes a second
mirror positioned adjacent to a second side of the gain medium and
positioned at an angle relative to the first polarizer and
configured to reflect the amplified signal beam received from the
gain medium to the first polarizer.
[0018] In related versions, the output comprises output optics for
outputting an amplified signal beam.
[0019] An exemplary embodiment of the present invention's method
for amplification of low intensity backscattered illumination
comprises the steps of inputting the light beam into an input of an
optical port when a controller set is in an OFF state, switching
the controller to an ON state to create an optical loop within the
optical port and an optical relay to trap the light beam,
amplifying the light beam through successive passes through the
optical loop, switching the controller to the OFF state to allow
the amplified light beam to be output, and outputting the amplified
light beam through an output of the optical port.
[0020] In related versions, the method further comprises, after
inputting the light beam into the input, propagating the light beam
through an optical relay to fill the optical relay with the light
beam.
[0021] In related versions, the method further comprises, after
propagating the light beam, outputting the light beam through the
output of the optical port.
[0022] In related versions, the input comprises input imaging
optics, the optical relay comprises a plurality of image formation
optics, and the output comprises output imaging optics.
[0023] An exemplary embodiment of the present invention's system
for amplification of low intensity backscattered illumination
comprises a system for amplifying a signal beam comprising an
amplifier device comprising an optical port having an input, an
output, and a controller having an ON state and an OFF state, the
controller connecting the input and the output to form an optical
loop in the ON state and disconnecting the input and the output in
the OFF state, and an optical relay housing the optical loop and
connected to the optical port having a gain medium configured for
amplifying the signal beam propagating inside the optical loop in
the ON state, a processor for processing the amplified signal beam
to generate an image, and a display for displaying the generated
image.
[0024] In related versions, the controller comprises an
electronically controlled wave plate having an ON state and an OFF
state.
[0025] In related versions, the amplifier device further comprises
a first polarizer positioned adjacent to a first side of the
electronically controlled wave plate and configured to reflect the
signal beam when the electronically controlled wave plate is in the
ON state, and a second polarizer positioned adjacent to a second
side of the electronically controlled wave plate and configured to
reflect the signal beam when the electronically controlled wave
plate is in the ON state.
[0026] In related versions, the amplifier device further comprises
a gain medium configured for receiving the signal beam and
amplifying the signal beam to produce an amplified signal beam, a
first mirror positioned adjacent to a first side of the gain medium
and at an angle relative to the second polarizer and configured to
reflect the signal beam from the second polarizer to the gain
medium, and a second mirror positioned adjacent to a second side of
the gain medium and positioned at an angle relative to the first
polarizer and configured to reflect the amplified signal beam
received from the gain medium to the first polarizer.
[0027] In related versions, the amplifier device further comprises
a first imaging lens positioned between the second polarizer and
the first mirror, and a second imaging lens positioned between the
first polarizer and the second mirror.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Other systems, methods, features and advantages of the
present invention will be or will become apparent to one of
ordinary skill in the art upon examination of the following figures
and detailed descriptions. It is intended that all such additional
apparatuses, systems, methods, features and advantages be included
within this description, be within the scope of the present
invention, and be protected by the appended claims. Component parts
shown in the drawings are not necessarily to scale, and may be
exaggerated to better illustrate the important features of the
present invention. In the drawings, like reference numerals
designate like parts throughout the different views, wherein:
[0029] FIG. 1A is a schematic diagram depicting an exemplary
embodiment of the present invention's device for imaging laser
amplification.
[0030] FIG. 1B is a schematic diagram depicting an exemplary
embodiment of the present invention's device for imaging laser
amplification.
[0031] FIG. 1C is a diagram depicting an exemplary embodiment of
the present invention's device for imaging laser amplification.
[0032] FIG. 2A is a schematic diagram depicting another exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification.
[0033] FIG. 2B is a schematic diagram depicting another exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification.
[0034] FIG. 2C is a schematic diagram depicting another exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification.
[0035] FIG. 3 is a schematic diagram depicting another exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification.
[0036] FIG. 4 is a schematic diagram depicting another exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification.
[0037] FIG. 5 is a schematic diagram depicting an exemplary
embodiment of the present invention's system for imaging laser
amplification.
[0038] FIG. 6 is a flowchart depicting an exemplary embodiment of
the present invention's method for imaging laser amplification.
DETAILED DESCRIPTION
[0039] FIG. 1A is a schematic diagram depicting an exemplary
embodiment of the present invention's device for imaging laser
amplification. The present invention's device represents a novel
way of amplifying a signal beam. The present invention's device
achieves this outcome by successively amplifying the signal beam
through a closed optical loop. Specifically, the present
invention's device incorporates optics components and a controller
for controlling opening and closing of the optical loop. The
exemplary embodiment of FIG. 1A captures these novel features of
the present invention's system.
[0040] In the exemplary embodiment of the present invention's
device in FIGS. 1A-1C, a device 100 has an optical relay 102
coupled to an optical port 104. The optical relay 102 comprises a
gain medium 106. The gain medium 106 can be any active laser medium
(e.g., a laser rod, semiconductor crystal, etc.) known in the art
for its ability to amplify the power of light typically in the form
of a light beam. The optical port 104 comprises a controller 108, a
first input port 110, a second input port 112, a first output port
114, and a second output port 116. The controller 108 can have an
ON state and an OFF state that rotates a polarization of a signal
beam that passes through.
[0041] Low intensity light scattered off of a laser illuminated
object and received by device 100 can be a signal beam 118. The
signal beam 118 can be backscattered light that includes image
information relating to the object. The signal beam 118 can
comprise a light beam. In related versions, the signal beam 118 can
further comprise an image of the object formed by the input and
output imaging optics of the optical relay 102. The signal beam 118
is received by the optical port 104 and passes through the first
input port 110 and the second input port 112 to the optical relay
102. When the controller 108 is in the OFF state, as depicted in
FIG. 1A, the signal beam 118 passes through the gain medium 106 and
back out through the second output port 116 and the first output
port 114. When the controller 108 is switched to the ON state, as
depicted in FIG. 1B, the first input port 110 becomes connected to
the first output port 114 and the second input port 112 becomes
connected to the second output port 116, trapping the signal beam
118 in a loop 120 between the optical port 104 and the optical
relay 102. While the signal beam 118 is trapped within the loop
120, the signal beam 118 repeatedly passes through the gain medium
106. This happens for as long as the controller 108 is in the ON
state. Switching the controller 108 back to the OFF state, as
depicted in FIG. 1C, reconnects the first input port 110 to the
second input port 112 and the first output port 114 to the second
output port 116, outputting an amplified signal beam 122.
[0042] Advantages include amplification of a signal beam with a
complex wavefront and an arbitrary wavelength within the bandwidth
of the gain medium without adjustment to longitudinal modes of the
cavity that forms the amplifying loop 120, reduction in pumping
power applied to the gain medium that results in a reduced level of
thermal load and a lower level of thermally induced aberrations,
allows control over amplification by controlling how many loops the
signal beam makes, amplification is not dependent on a high
amplification from a single round trip, and saves space because
optical elements that comprise the loop do not have to be
recurrent. Thus, the approach described herein allows for
amplification of laser pulses with no limits on their spectral
composition. It can therefore be useful for a broad range of
applications where intensity enhancement of a wide-angle signal is
of interest, such as the amplification of low-intensity coherent
images in space surveillance, microscopy, biology, etc.
[0043] Additionally, as will be described in greater detail below,
optical conditioning elements can be incorporated into the optical
relay 102 to reduce signal noise and produce a cleaner signal.
[0044] FIGS. 2A-2C are schematic diagrams depicting an exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification. As shown in FIG. 2A, a
signal beam 206 can be received at an optical port 208 from a
different direction than in FIG. 1. The optical port 208 can
comprise a controller 210 comprising a half-wave plate 200, an
angular selector 222, and an electronically controlled wave plate
212. The electronically controlled wave plate 212 can be any
electronically controlled wave plate known in the art, such as a
Pockels cell, with an ON state and an OFF state that rotates a
polarization of a signal beam that passes through. The ON state and
OFF state of the electronically controlled wave plate 212
corresponds to the ON state and the OFF state of the controller
210. The half-wave plate 200 can be any wave plate known in the art
that shifts a polarization of a signal beam by 180 degrees. The
angular selector 222 is for limiting a field of view (FOV) of the
device 200 to suppress noise associated with amplified spontaneous
emission (ASE). The controller 210 can be positioned within the
optical port 208 between a first polarizer 202 and a second
polarizer 204. The first polarizer 202 and the second polarizer 204
can be any polarizer known in the art, such as an optical filter
that passes light of a specific polarization and blocks waves of
other polarizations. In some versions, the first polarizer 202, the
half-wave plate 200, the electronically controlled wave plate 212,
and the second polarizer 204 can be arranged in a straight line, as
depicted in FIGS. 2A-2C.
[0045] When the electronically controlled wave plate 212 is in the
OFF state, thus also putting the controller 210 in the OFF state,
as depicted in FIG. 2A, the signal beam 206 has a polarization that
causes it to pass through the first polarizer 202. The polarization
of the signal beam 206 is then shifted 180 degrees by the half-wave
plate 200, and is reflected by the second polarizer 204 into the
optical relay 214. The signal beam 206 passes through a gain medium
216 and is reflected by the first polarizer 202 through the
half-wave plate 200, where the polarization of the signal beam 206
is once again shifted 180 degrees by the half-wave plate 200 so
that the signal beam 206 passes through the second polarizer 204.
In all, the signal beam 206 makes only one pass through the gain
medium 216 of the optical relay 214 before exiting out from the
optical port 208.
[0046] When the electronically controlled wave plate 212 is
switched to the ON state, thus also putting the controller 210 in
the ON state, as depicted in FIG. 2B, the controller 210 shifts the
polarization of the signal beam 206 so that it becomes trapped in a
loop 218 for as long as the controller 210 is in the ON state. As a
result, the signal beam 206 makes multiple passes through the gain
medium 216, as well as the other above-described components, for
amplification and conditioning of the signal beam 206.
[0047] When the electronically controlled wave plate 212 is
switched back to the OFF state, also putting the controller 210
back in the OFF state, as depicted in FIG. 2C, the polarization of
the signal beam 206 is no longer shifted for continuous passes
through the loop 218, and an amplified signal beam 220 is
outputted.
[0048] FIG. 3 is a schematic diagram depicting an exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification. The device 300 can comprise
an optical port 302 coupled to an optical relay 304. The optical
port 302 can further comprise a controller 306 positioned between a
first polarizer 312 and a second polarizer 314. The controller 306
can comprise a half-wave plate 308 and an electronically controlled
wave plate 310, similar to what is described and depicted above in
FIGS. 2A-2C. The optical port 302 can also comprise an input port
316, output port 322, and input optics 318. The input port 316 and
the output port 322 can be apertures defined by optical port 302,
and input optics 318 can be an optical lens as known in the art for
conditioning a signal beam 320. In some versions, the input port
316, input optics 318, first polarizer 312, half-wave plate 308,
electronically controlled wave plate 310, second polarizer 314, and
output port 322 can be arranged in a straight line, as shown in
FIG. 3.
[0049] The optical relay 304 can comprise a first imaging lens 322,
a second imaging lens 324, a first mirror 326, a second mirror 328,
and a gain medium 330. The first imaging lens 322 and the second
imaging lens 324 can comprise optical repeaters having a pair of
concentric lenses 322a and 322b, and 324a and 324b, such that
lenses 322a and 324a have a same focal point f1, and 322b and 324b
have a same focal point f2. The second imaging lens 324 can further
comprise a diaphragm 334 positioned between lenses 324a and 324b
for limiting an amount of light that passes through.
[0050] The device 300 functions substantially similar to what has
been described above. When the controller is in the OFF state, the
signal beam 320 passes through the input port 316, input optics
318, the first polarizer, the half-wave plate 306, and the
electronically controlled wave plate 310 in that order. Because a
polarization of the signal beam 320 is rotated 180 degrees by the
half-wave plate 306, the signal beam is reflected by the second
polarizer 314 through the second repeater 324 to the first mirror
326. The first mirror 326 then reflects the signal beam 320 through
the gain medium 330 and to the second mirror 328, where the signal
beam 320 is reflected back to the first polarizer 312. The first
polarizer 312 then reflects the signal beam 320 through the
half-wave plate 306 to rotate the polarization of the signal beam
320 180 degrees so that the signal beam 320 it outputted through
the output port 322.
[0051] When the controller 306 is in the ON state, the
electronically controlled wave plate shifts the polarization of the
signal beam 320 such that the signal beam 320 becomes trapped
within optical loop 334 that is defined by the optical elements of
the optical port 302 and the optical relay 304. Through successive
passes through the gain medium 330, the signal beam 320 becomes
amplified. When the controller 360 is switched back to the OFF
state, an amplified signal beam 333 is outputted through the output
port 322.
[0052] FIG. 4 is a schematic diagram depicting an exemplary
embodiment of an alternative version of the present invention's
device for imaging laser amplification. The main difference between
device 400 and device 300 is that the first and second repeaters
and gain medium are positioned between the first and second
polarizers. An advantage of the device of FIG. 4 over the other
described versions is that the angle of view can potentially be
narrowed using this arrangement.
[0053] For example, signal beam 402 enters optical port 404 through
input port 406 and passes through input optics 408, first polarizer
410, first repeater 412, electronically controlled wave plate 414
in the OFF state, second repeater 416, gain medium 418, and second
polarizer 420, and outputted through output port 422. When the
electronically controlled wave plate is switched to the ON state,
the signal beam 402 becomes trapped within loop 424 such that the
signal beam 402 makes successive passes through the gain medium
418. The signal beam 402 passes through the optical components of
the optical relay 426 and is reflected by the second polarizer 420
toward a first mirror 428 positioned within the optical relay 426.
The first mirror 428 then reflects the signal beam towards a second
mirror 430, also positioned within the optical relay 426. The
second mirror 430 then reflects the signal beam 402 back to the
first polarizer 410 positioned within the optical port 406, where
the signal beam completes the loop 424. Switching the
electronically controlled wave plate to the OFF state allows
outputting of an amplified signal beam 432.
[0054] As depicted in FIG. 4, the electronically controlled wave
plate 414, and the gain medium 418, can potentially narrow the
angle of view and thus are positioned between the first repeater
412 and the second repeater 416. The input optics 408 forms a
remote object image on the first repeater 412.
[0055] The scheme shown in FIG. 4 allows the amplifier's angle of
view increased to the maximum value determined by the geometrical
size of the electronically controlled wave plate 414 and the gain
medium 418 according to the following equation:
.theta..sub.AV=D.sub.OEn.sub.OE/L.sub.OE, (1)
[0056] where D.sub.OE n.sub.OE, and L.sub.OE are respectively, the
diameter, the refractive index, and the length of the optical
element, and .theta..sub.AV is the angle of view.
[0057] The number of resolved elements in an amplified image (m) is
determined by the ratio of the amplifier's angle of view and
diffraction on the optical element's aperture:
m = .theta. AV .theta. d = D OE 2 n OE 1.22 .lamda. L OE = n OE
1.22 N Fr , ( 2 ) ##EQU00001##
[0058] where .lamda. is the wavelength of the signal beam 402. It
follows from Eq. (2) that the number of the resolved elements in
the amplified image is determined by the Fresnel number (N.sub.Fr)
of the optical element. Therefore, the amplifier's angle of view is
determined by the optical element with the lowest Fresnel
number.
[0059] FIG. 5 is a schematic diagram depicting an exemplary
embodiment of the present invention's system for imaging laser
amplification. System 500 can comprise an amplifier device 502
having an optical port 504, and an optical relay 506, a processor
508, and a display 510. The processor 508 and display 510 can be a
computer and monitor as well-known in the art.
[0060] The optical port 504 can comprise an input port 522, an
input lens 512, a first polarizer 514, a half-wave plate 516, an
angular selector 518, an electronically controlled wave plate 520
having an ON state and an OFF state, a second polarizer 524, and an
output port 526.
[0061] The optical relay can comprise a first imaging lens 530, a
first mirror 532, a gain medium 534, a second mirror 536, and a
second imaging lens 538. The first imaging lens 530 and the second
imaging lens 538 can comprise a pair of concentric imaging lenses
as described above with corresponding focal points. The gain medium
534 can be any lasing medium known in the art and described above
for amplification of a laser signal.
[0062] When the electronically controlled wave plate 520 is in the
OFF state, a signal beam 528 can be received by the amplifier 502
makes one loop 540 through the optical elements, pursuant to the
descriptions above. The signal beam 528 can be backscattered light
containing information regarding an image of an object. When the
electronically controlled wave plate 520 is switched to the ON
state, the signal beam 528 becomes trapped within the loop 540 and
is amplified by successive trips through the gain medium 534. When
the electronically controlled wave plate 520 is switched back to
the OFF state, an amplified signal beam 542 is outputted from the
amplifier device 502. The amplified signal beam 542 is then
received by the processor 508 and processed to create an image of
an object. The image is then displayed on the display 510. The
image can be a live video feed of the object.
[0063] In related versions, the amplified signal beam 542 can have
two components: the amplified signal and the amplified spontaneous
emission (ASE). Two possible scenarios of the amplified signal beam
542 can result: (i) P.sub.S>>P.sub.ASE, and (ii)
P.sub.S.ltoreq.P.sub.ASE, where P.sub.S is the power of the signal
beam 528 and P.sub.ASE is the power of the ASE after a single round
trip through the gain medium 534. In case (i), the ASE does not
affect the amplified signal, but in case (ii), the amplified signal
is separated from the ASE. This can be achieved by applying the
phase conjugate mirror (PCM) technique with its implementation in a
Brillouin-enhanced four-wave mixing (BEFWM) scheme, as known in the
art, to generate a phase conjugate beam 544. The PCM technique and
the BEFWM method may be executed at the processor 508.
[0064] The resulting phase conjugate beam 544 contains the ASE and
is backward reflected and injected into the output port 526 of the
amplifier device 502. When the electronically controlled wave plate
is in the ON state, the phase conjugate beam 544 propagates through
reverse loop 546 in an opposite direction as loop 540, and the
phase conjugate beam 544 circulates the same number of round trips
as the original signal beam 528. In this way, the phase conjugate
beam 544 compensates for aberrations resulting from amplification
of the signal beam 528, and then is further amplified and pulled
out of the cavity though input lens 512 and input port 522, after
the electronically controlled wave plate is turned OFF. Upon its
exit, the phase conjugate beam 544 reconstructs the structure of
signal beam 528 with phase conjugation and amplification.
[0065] FIG. 6 is a flowchart depicting an exemplary embodiment of
the present invention's method for imaging laser amplification.
This present invention's method, such as method 600, provides the
ability to amplify a signal beam through successive loops in an
optical cavity.
[0066] As shown in FIG. 6, method 600 comprises steps 602 to 610.
At step 602, a light beam is received by the laser amplifier device
through an input of an optical port when a controller set in an OFF
state. Various exemplary embodiments of the present invention's
optical port and controller, as depicted in FIGS. 1A-5 and
described above. In related versions, the input can comprise input
imaging optics.
[0067] At step 604, the controller is switched to an ON state to
create an optical loop within the optical port and an optical relay
to trap the light beam. In related versions, the optical relay can
comprise a plurality of image formation optics.
[0068] At step 606, the light beam is amplified through successive
passes through the optical loop. A number of passes can be
determined by how much amplification is needed to generate a clear
image. A greater number of passes will yield a higher level of
amplification of the signal beam. In related versions, the number
of passes can be monitored and adjusted to generate a clear image
from the light beam. For example, an incremental power of the
signal beam is monitored as it circulates inside the closed
loop.
[0069] At step 608, the controller is switched to the OFF state to
allow the amplified light beam to be output. In related versions,
the controller can comprise an electronically controlled wave plate
with an ON state and an ON state and a half-wave plate.
[0070] At step 610 the amplified light beam is output through an
output of the optical port. In related versions, the output can
comprise output imaging optics to condition the amplified output
signal.
[0071] In related versions, the method can further include, after
inputting the light beam into the input, propagating the light beam
through an optical relay to fill the optical relay with the light
beam.
[0072] In related versions, the method can further include, after
propagating the light beam, outputting the light beam through the
output of the optical port.
[0073] Exemplary embodiments of the invention have been disclosed
in an illustrative style. Accordingly, the terminology employed
throughout should be read in a non-limiting manner. Although minor
modifications to the teachings herein will occur to those well
versed in the art, it shall be understood that what is intended to
be circumscribed within the scope of the patent warranted hereon
are all such embodiments that reasonably fall within the scope of
the advancement to the art hereby contributed, and that that scope
shall not be restricted.
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