# US 5,351,250 A · Optical beam steering device

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- Number: US 5,351,250 A
- Document ID: US5351250A
- Status: Granted
- Kind: A
- Application number: 07/768,960
- Filed: 1991-10-21
- Granted: 1994-09-27
- Earliest claimed: 1989-04-27
- Assignees: The Secretary of State for Defence in Her Majesty's Government of the United Kingdom of Great Britain and Northern Ireland
- Inventors: Andrew M. Scott
- Web page: https://patentgrep.com/patent/US5351250A

## CPC

- G02F 1/3538: {for optical phase conjugation (controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation using optical phase conjugation H01S3/10076)}
- H01S 3/101: Lasers provided with means to change the location from which, or the direction in which, laser radiation is emitted
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

An optical beam steering device (10) incorporates a laser (12), three Brillouin shifters (22 to 26, 44 to 48, 54 to 58), a four wave mixing cell (40) and a low power beam steering device (62). The first shifter (22 to 26) and the mixing cell (40) contain TiCl.sub.4, and the other shifters (44 to 48, 54 to 58) contain 20% CCl.sub.4 /80% CS.sub.2. The first and third shifters (22 to 26, 54 to 58) frequency downshift the laser beam (16) by .delta..upsilon..sub.A and .delta..upsilon..sub.B respectively. Light (16') from the first shifter (22 to 26) is amplified and provides a first pump beam input to the mixing cell (40). It then passes to the second shifter (44 to 48), for frequency downshifting by .delta..upsilon..sub.B and returns as a second cell pump beam ( 16"). Light (18') from the third shifter (54 to 58) passes via the low power beam steering device (62) to the cell (40) as a weak input signal beam (18"). The cell (40) responds to the pump beams (16', 16") and signal beam (18") by generating a high power beam (68) which is a phase conjugate of the signal beam (18") and retraces part of its steered path.

## Claims

### Claim 1

An optical steering device including:
delivering means for providing a low power light beam;
means for steering said low power light beam relative to said delivering means; and
phase conjugating means, responsive to the steered low power light beam, for generating a high power phase conjugate of said low power light beam wherein the phase conjugating means includes a Brillouin four wave mixing cell and said cell comprising a means for providing Brillouin four wave mixing; and
pumping means for providing the phase conjugating means with counterpropagating laser pump beams having frequencies for producing four wave mixing in combination with the steered low power beam.

### Claim 2

An optical steering device including:
means for steering a low power light beam; and
phase conjugating means arranged to receive the steered low power beam and to generate a high power phase conjugate thereof, said phase conjugating means includes a Brillouin four wave mixing cell and pumping means for providing the cell with counterpropagating laser pump beams having frequencies appropriate to produce four wave mixing in combination with the steered low power beam, wherein the pumping means is also arranged to provide the steering means with a low power light beam.

### Claim 3 (depends on 2)

A device according to claim 2 wherein pumping means comprises:
(1) a laser
(2) a first Brillouin scattering cell arranged to receive part of the laser output and reduce its frequency by a decrement .delta..upsilon..sub.A to provide a first pump beam input to the four wave mixing cell,
(3) a second Brillouin scattering cell arranged to receive a further part of the laser output, to reduce its frequency by a decrement .delta..upsilon..sub.B and relay the frequency reduced laser output to the steering means input, and
(4) a third Brillouin scattering cell arranged to receive the first pump beam after transmission through the four wave mixing cell, and to return it with a further frequency decrement .delta..upsilon..sub.B as a second pump beam.

### Claim 4 (depends on 3)

A device according to claim 3 wherein an amplifier is arranged to amplify the first pump beam prior to input to the four wave mixing cell (40).

### Claim 5

An optical steering device including:
(1) steering means for producing a steered low power light beam;
(2) a Brillouin four wave mixing cell, responsive to the steered low power beam, for generating a high power phase conjugate thereof; and
(3) pumping means for providing said mixing cell with counterpropagating pump beams having frequencies, said pump beams frequencies comprising a means for producing four wave mixing in combination with said steered low power beam; and
(4) said pumping means including means for providing the steering means with a low power light beam.

### Claim 6 (depends on 5)

A device according to claim 5, wherein said pumping means comprises:
(1) a laser having an output frequency;
(2) a first Brillouin scattering cell, responsive to at least a portion of said laser output, for reducing said output frequency by a decrement .delta..upsilon..sub.A, and for providing a first pump beam input to said four wave mixing cell;
(3) a second Brillouin scattering cell, responsive to at least a portion of said laser output, for reducing said output frequency by a decrement .delta..upsilon..sub.B and for relaying said decrement .delta..upsilon..sub.B frequency reduced laser output to the steering means input; and
(4) a third Brillouin scattering cell, responsive to said first pump beam after transmission through the said four wave mixing cell, for returning said first pump beam with a further frequency decrement .delta..upsilon..sub.B as a second pump beam.

### Claim 7 (depends on 6)

A device according to claim 6, further including an amplifier comprising means for amplifying said first pump beam prior to input to said four wave mixing cell.

### Claim 8

An optical steering device comprising:
(1) means for producing a steered low power light beam; and
(2) phase conjugating means, responsive to the steered low power beam, for generating a high power phase conjugate of said low power beam, said phase conjugating means including a Brillouin four wave mixing cell and pumping means for providing said mixing cell with counterpropagating pump beams, said pump beams frequencies comprising a means for producing four wave mixing in combination with said steered low power beam.