US4767195A
Expired / Lapsed
US
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System and method for encoding information onto an optical beam
Assignee: Raytheon Co
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Filing: 1986-03-21
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Granted: 1988-08-30
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Expires: 2006-03-21
Abstract
Abstract A system and method for encoding information onto an optical beam is described in which a photorefractive material is used to modulate the beam. An alternating electric field is applied to the photorefractive material and modulated so as to vary the material's index ellipsoid via the electro-optic effect and hence modulate an output beam in accordance with the information to be encoded. The invention has applications to both externally pumped and self-pumped phase conjugate mirrors, and to other optical systems. Various modulation techniques can be used, and the modulation can be isolated from noisy beams by applying the modulating electric field on a high frequency carrier.
Inventors
- 👤 David M. Pepper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:56
CPC Classifications
G; G02; G02B; G02B27/00; G02F; G02F1/00; G02F1/35; G02F1/353; G02F1/3536; G02F1/3538; G02B5/00; G02B5/20; G02B5/22; G02B5/23; G02F1/01; G02F1/03; G02F1/05; G02F1/0541
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
77 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive an input optical beam, means for establishing photorefractive gratings within said body to produce a phase conjugate output beam in response to an input optical beam, means for establishing an alternating electric field within the body concurrently with said photorefractive gratings, and means for modulating said electric field relative to said body to encode said phase conjugate output beam.
Claim 2
Independent Claim
77 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive an input optical beam, means for establishing photorefractive gratings within said body to produce a phase conjugate output beam in response to an input optical beam, means for establishing an alternating electric field within the body concurrently with said photorefractive gratings, and means for modulating said electric field relative to said body to encode said phase conjugate output beam.
Claim 3
Dependent Claim
53 words
The system of claim 1, the means for establishing an alternating electric field comprising means for establishing the field with an alternating frequency substantially higher than the noise bandwidth of the input beam, the field thereby providing a higher frequency carrier to substantially isolate the modulation from noise in the beam frequency range.
Claim 4
Dependent Claim
21 words
The system of claim 1, wherein the means for modulating the alternating electric field comprises means for modulating the alternation frequency.
Claim 5
Dependent Claim
21 words
The system of claim 1, wherein the means for modulating the alternating electric field comprises means for modulating the alternation phase.
Claim 6
Dependent Claim
21 words
The system of claim 1, wherein the means for modulating the alternating electric field comprises means for modulating the alternation amplitude.
Claim 7
Dependent Claim
40 words
The system of claim 1, the photorefractive material comprising a two-wave phase conjugate mirror medium, wherein the means for modulating the alternating electric field relative to said body comprises means for modulating the polarization of said phase conjugate output beam.
Claim 8
Dependent Claim
20 words
The system of claim 1, further comprising means for modulating the electric field with a plurality of multiplexed modulation signals.
Claim 9
Independent Claim
55 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive an optical beam, means for inducing photorefractive gratings within said body, and means for modulating the body's index ellipsoid via the electro-optic effect concurrently with said photorefractive gratings to encode an optical beam diffracted by the body.
Claim 10
Independent Claim
55 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive an optical beam, means for inducing photorefractive gratings within said body, and means for modulating the body's index ellipsoid via the electro-optic effect concurrently with said photorefractive gratings to encode an optical beam diffracted by the body.
Claim 11
Dependent Claim
44 words
The system of claim 8, the modulating means being adapted to modulate the body's index ellipsoid via the electro-optic effect at a substantially higher frequency range than the beam noise bandwidth, and thereby substantially isolate the modulation from noise in the beam frequency range.
Claim 12
Independent Claim
97 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive a first optical beam, means for applying at least one second optical beam to the body to cross-couple with the first beam within the body and produce a resultant output beam, means for establishing an alternating electric field within the body to induce a variance in the index ellipsoid via the electro-optic effect of the body upon the output beam, and means for modulating the alternating electric field within the body to encode desired information onto the output beam.
Claim 13
Independent Claim
97 words
A system for encoding information onto an optical beam, comprising: a body of photorefractive material adapted to receive a first optical beam, means for applying at least one second optical beam to the body to cross-couple with the first beam within the body and produce a resultant output beam, means for establishing an alternating electric field within the body to induce a variance in the index ellipsoid via the electro-optic effect of the body upon the output beam, and means for modulating the alternating electric field within the body to encode desired information onto the output beam.
Claim 14
Dependent Claim
58 words
The system of claim 10, for use with a noisy first optical beam, wherein the alternating field means is adapted to establish an alternating electric field at a substantially higher frequency of alternation than the laser beam noise frequency, thereby providing a higher frequency carrier to substantially remove the modulating signal from the noise associated with the beam.
Claim 15
Dependent Claim
30 words
The system of claim 10, said photorefractive body and second beam means comprising a phase conjugate mirror (PCM) with the output beam comprising a phase conjugate of the first beam.
Claim 16
Dependent Claim
27 words
The system of claim 12, the second beam means comprising means for applying a pair of pump beams to the body to establish a four-wave mixer PCM.
Claim 17
Dependent Claim
63 words
The system of claim 12, the means for applying a second optical beam to the body comprising means for returning the first beam through the body at a return angle to the first beam path within the body which is sufficiently small to induce the formation of the output beam as a phase conjugate of the first beam, whereby the PCM is self-pumped.
Claim 18
Dependent Claim
33 words
The system of claim 14, wherein the photorefractive material is a semiconductor, and the magnitude and frequency of the alternating electric field increases the optical gain of the photorefractive material to enable self-pumping.
Claim 19
Dependent Claim
43 words
The system of claim 15, wherein the modulating means produces a modulating signal within a substantially higher frequency range than the frequency of field alternation, thereby encoding information onto the phase conjugated output beam substantially through modulation of the photorefractive material's electro-optic effect.
Claim 20
Dependent Claim
45 words
The system of claim 15, wherein the modulating means produces a modulating signal within the frequency regime of the field alternation, thereby encoding information onto the phase conjugated output beam by modulating both the photorefractive material's index ellipsoid via the electro-optic effect and photorefractive response.
Claim 21
Dependent Claim
57 words
The system of claim 12, the modulating means providing information to be remotely sensed, further comprising optical fiber means arranged to transmit the first beam to the photorefractive body and to receive the phase conjugated output beam, thereby enabling the output beam to be transmitted through the optical fiber means to a remote location from the PCM.
Claim 22
Dependent Claim
77 words
The system of claim 12, further comprising a second PCM of similar construction to the first PCM with an associated means for establishing an alternating electric field within the body of the second PCM at a frequency substantially equal to the unmodulated alternating field frequency for the first PCM, and means for sensing frequency differences between the phase conjugated output beams of the two PCMs to detect the modulation applied to alternating field for the first PCM.
Claim 23
Dependent Claim
56 words
The system of claim 12, further comprising an apertured mirror spaced from the PCM and a laser gain medium between the mirror and PCM, the mirror, PCM and gain medium comprising a phase conjugate laser, wherein the modulating means is adapted to modulate the electric field within the PCM's photorefractive body at a mode locking frequency.
Claim 24
Dependent Claim
68 words
The system of claim 10, implemented as a variable gain image amplifier, wherein the first optical beam contains an image to be amplified, a two-wave mixing means is provided to cross-couple the second optical beam with the first beam to provide an energy transfer to the first beam, and the field modulating means is adapted to encode the transfer of energy from the first to the second beam.
Claim 25
Dependent Claim
93 words
A self-pumped phase conjugate mirror (PCM), comprising: a crystal formed from a photorefractive material adapted to receive a first laser beam, means for applying an alternating electric field across the crystal, said field being selected to establish a photorefractive index grating shift of about 90° within the crystal, means for returning the first beam to the crystal at a return angle to the first beam path within the body at which a phase conjugated output beam is produced, and means for modulating the alternating electric field to encode information onto the output beam.
Claim 26
Dependent Claim
93 words
A self-pumped phase conjugate mirror (PCM), comprising: a crystal formed from a photorefractive material adapted to receive a first laser beam, means for applying an alternating electric field across the crystal, said field being selected to establish a photorefractive index grating shift of about 90° within the crystal, means for returning the first beam to the crystal at a return angle to the first beam path within the body at which a phase conjugated output beam is produced, and means for modulating the alternating electric field to encode information onto the output beam.
Claim 27
Dependent Claim
57 words
The self-pumped PCM of claim 22, wherein the modulating means is adapted to modulate the electric field at a substantially higher frequency than the frequency of the photorefractive response, and thereby encode the output beam by means of modulations in the crystal's index ellipsoid via the electro-optic effect with the crystal's photorefractive-induced index grating remaining substantially stationary.
Claim 28
Independent Claim
71 words
A method of encoding information onto an optical beam, comprising: establishing an alternating electric field within a body of photorefractive material, establishing photorefractive gratings within said body concurrently with said field, while transmitting an input optical beam into the body, operating upon the input beam within the body to establish a phase conjugate output beam, and modulating the electric field relative to said body to encode said phase conjugate output beam.
Claim 29
Independent Claim
71 words
A method of encoding information onto an optical beam, comprising: establishing an alternating electric field within a body of photorefractive material, establishing photorefractive gratings within said body concurrently with said field, while transmitting an input optical beam into the body, operating upon the input beam within the body to establish a phase conjugate output beam, and modulating the electric field relative to said body to encode said phase conjugate output beam.
Claim 30
Dependent Claim
38 words
The method of claim 24, wherein the alternating field frequency is substantially greater than the input beam's noise frequency bandwidth, thereby providing a higher frequency carrier to substantially isolate the modulation from noise in the beam frequency range.
Claim 31
Dependent Claim
16 words
The method of claim 24, wherein the electric field is modulated by modulating its alternation frequency.
Claim 32
Dependent Claim
16 words
The method of claim 24, wherein the electric field is modulated by modulating its alternation phase.
Claim 33
Dependent Claim
25 words
The method of claim 24, wherein the electric field is modulated relative to said body by modulating the polarization of said phase conjugate output beam.
Claim 34
Dependent Claim
8 words
The method of claim 24, wherein the electric
Claim 35
Independent Claim
53 words
A method of encoding information onto an optical beam, comprising: inducing photorefractive gratings within a body of photorefractive material, while transmitting an input optical beam into said body, diffracting said input beam within the body by said gratings, and modulating the body's index ellipsoid via the electroptic effect to encode the diffracted beam.
Claim 36
Independent Claim
53 words
A method of encoding information onto an optical beam, comprising: inducing photorefractive gratings within a body of photorefractive material, while transmitting an input optical beam into said body, diffracting said input beam within the body by said gratings, and modulating the body's index ellipsoid via the electroptic effect to encode the diffracted beam.
Claim 37
Dependent Claim
41 words
The method of claim 30, wherein the body's index ellipsoid is modulated via the electro-optic effect at a substantially higher frequency range than the input beam's noise frequency spectrum, thereby substantially isolating the modulation from noise in the beam frequency range.
Claim 38
Independent Claim
89 words
A method of encoding information onto an optical beam, comprising: transmitting a first optical beam through a body of photorefractive material, establishing an alternating electric field within the body to induce a variance in the body's index ellipsoid via the electro-optic effect, applying at least one second optical beam to the body to cross-couple with the first beam and produce a resultant output beam, and modulating the alternating electric field to encode desired information onto the output beam through variations in the body's index ellipsoid via the electrooptic effect.
Claim 39
Independent Claim
89 words
A method of encoding information onto an optical beam, comprising: transmitting a first optical beam through a body of photorefractive material, establishing an alternating electric field within the body to induce a variance in the body's index ellipsoid via the electro-optic effect, applying at least one second optical beam to the body to cross-couple with the first beam and produce a resultant output beam, and modulating the alternating electric field to encode desired information onto the output beam through variations in the body's index ellipsoid via the electrooptic effect.
Claim 40
Dependent Claim
65 words
The method of claim 32, wherein the photorefractive index grating shift within the body of about 90°, and the application of the second beam to the body comprises returning the first beam through the body at a return angle to the first beam to produce an output beam as a phase conjugate of the first beam, thereby providing self-pumped conjugate reflection of the first beam.
Claim 41
Dependent Claim
40 words
The method of claim 32, wherein the electric field alternation is substantially higher rate than the body's photorefractive response time, the field modulation thereby encoding the output beam by modulating the body's electro-optic effect without substantially shifting its index gratings.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-30 | 1992-02-29 | 1992-08-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-30 | 1996-02-29 | 1996-08-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-30 | 2000-02-29 | 2000-08-30 | $7700.00 | Window Closed / Lapsed |