Patent US4508431A successfully refreshed from Google Patents.
US4508431A
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Photorefractive laser beamsteering device
Assignee: Massachusetts Institute of Technology
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Filing: 1982-01-11
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Granted: 1985-04-02
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Expires: 2002-01-11
Abstract
Abstract Apparatus for steering a principal beam of electromagnetic radiation consisting of a photorefractive material situated such that the principal beam of radiation passes therethrough, the material being photoconductive and having an index of refraction that is variable in response to transverse electro-optical effects; and variable writing means for irradiating the material in a direction orthogonal to the principal beam with two beams which intersect at a variable angle so as to write a diffraction grating in the material and thereby vary the index of refraction of the material, thus steering the principal beam.
Inventors
- 👤 Philip D. Henshaw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:38
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/29; G02F1/293
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
130 words
Apparatus for steering a principal beam of electromagnetic radiation comprising: A. a photorefractive material situated such that said principal beam passes therethrough, said photorefractive material being photoconductive and having an index of refraction that is variable in response to transverse electro-optical effects, and B. variable writing means for irradiating said photorefractive material with at least two beams which intersect one another and which are each transverse to the principal beam so as to write a diffraction grating in said photorefractive material and thereby vary the index of refraction of said photorefractive material, wherein the angle at which said two beams intersect is variable such that for a desired angle of deflection said diffraction grating is formed at about an angle set by Bragg's law so as to optimize steering efficiency.
Claim 2
Dependent Claim
130 words
Apparatus for steering a principal beam of electromagnetic radiation comprising: A. a photorefractive material situated such that said principal beam passes therethrough, said photorefractive material being photoconductive and having an index of refraction that is variable in response to transverse electro-optical effects, and B. variable writing means for irradiating said photorefractive material with at least two beams which intersect one another and which are each transverse to the principal beam so as to write a diffraction grating in said photorefractive material and thereby vary the index of refraction of said photorefractive material, wherein the angle at which said two beams intersect is variable such that for a desired angle of deflection said diffraction grating is formed at about an angle set by Bragg's law so as to optimize steering efficiency.
Claim 3
Dependent Claim
30 words
The apparatus of claim 1 wherein the apparatus further comprises bias means for applying a voltage across said photorefractive material and thereby making photoconduction in said photorefractive material more rapid.
Claim 4
Dependent Claim
93 words
The apparatus of claim 1 wherein the variable writing means further comprises: A. An array of lasing media, B. selector means for separately activating each lasing medium so as to produce coherent radiation, C. beam splitting means orthogonal to said array, for splitting the radiation from any one of the lasing media into a first and second writing beam, D. lens means for collimating and focusing the split beams to interfere in the photorefractive material, whereby diffraction gratings of different periods can be formed by selecting a particular lasing medium from the array.
Claim 5
Dependent Claim
15 words
The apparatus of claim 3 wherein said array is an array of discrete lasing materials.
Claim 6
Dependent Claim
30 words
The apparatus of claim 3 wherein said array is a continuous stripe of lasing material, particular regions of which are capable of emitting radiation when activated by the selector means.
Claim 7
Dependent Claim
36 words
The apparatus of claim 4 wherein the selector means comprises an electromagnetically controlled electron beam whereby a variable electromagnetic field is employed to deflect an electron beam onto a particular medium and to thereby induce lasing.
Claim 8
Dependent Claim
36 words
The apparatus of claim 5 where the selector means comprises an electromagnetically controlled electron beam whereby a variable electromagnetic field is employed to deflect an electron beam onto a particular medium and to thereby induce lasing.
Claim 9
Dependent Claim
13 words
The apparatus of claim 3 wherein the lasing media are cadmium sulfide semiconductors.
Claim 10
Dependent Claim
28 words
The apparatus of claim 2 wherein said principal beam is a high-power, long-wavelength laser beam and the first and second writing beams are low-power, short wavelength laser beams.
Claim 11
Dependent Claim
98 words
The apparatus of claim 1 wherein the variable writing means further comprises: A. a rotatable polygon with mirrored sides, B. a source of variable frequency, pulsed radiation directed upon the polygon, C. beam splitting means orthogonal to the axis of rotation of the polygon; for splitting the radiation reflected from the polygon into a first and second writing beam, and D. lens means for collimating and focusing the split beams to interfere in the photorefractive material, whereby the diffraction gratings of different periods can be formed by timing of the laser pulse relative to the polygonal mirror position.
Claim 12
Dependent Claim
13 words
The apparatus of claim 1 wherein said photorefractive material is bismuth silicon oxide.
Claim 13
Dependent Claim
13 words
The apparatus of claim 1 wherein said photorefractive material is bismuth germanium oxide.
Claim 14
Dependent Claim
12 words
The apparatus of claim 1 wherein said photorefractive material is lithium niobate.
Claim 15
Dependent Claim
12 words
The apparatus of claim 1 wherein said photorefractive material is zinc selenide.
Claim 16
Dependent Claim
13 words
The apparatus of claim 1 wherein said photorefractive material is potassium tantalum niobate.
Claim 17
Dependent Claim
13 words
The apparatus of claim 1 wherein said photorefractive material is strontium barium niobate.
References Cited (Backward Citations)
US3539244A
Cited
US3790252A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-04-01 | 1988-10-01 | 1989-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-04-01 | 1992-10-01 | 1993-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-04-01 | 1996-10-01 | 1997-04-02 | $7700.00 | Window Closed / Lapsed |