Coherent beam combination (CBC) systems and methods

Patent metadata

Field	Value
Publication number	US-11973305-B2
Application number	US-201917259933-A
Country	US
Kind code	B2
Filing date	Jul 18, 2019
Priority date	Jul 19, 2018
Publication date	Apr 30, 2024
Grant date	Apr 30, 2024

Abstract

A coherent beam combination (CBC) system (10) includes an array of beam sources (12a, 12b and 12c) generating coherent beams directed towards a target (T). The phase modulators (14a, 14b and 14c) allow adjustment of relative phase offsets of the beams. A detector (16) monitors an intensity of the radiation impinging on an area of the target (T). A controller (18) receives the intensity parameter and controls a phase adjustment of the beams according to a deterministic (i.e., quantitative) measurement of a phase offset of each beam relative to a representative phase of the sum of all the other beams. This is achieved by using interferometric techniques, referred to herein as Target In-the-Loop Interferometry (TILI).

First claim

What is claimed is:

1. A method of determining phase offsets of multiple transmitted beams of a coherent beam combination (CBC) device impinging on a target, each of the transmitted beams being transmitted by an associated beam source having a corresponding adjustable phase modulator, the method comprising:
(a) for each of said transmitted beams, actuating the corresponding adjustable phase modulator to modulate a current phase of the transmitted beam between at least three phase states;
(b) while each adjustable phase modulator is actuated, monitoring an intensity parameter that varies as a function of an intensity of radiation of the transmitted beam impinging on the target;
(c) identifying variations in the intensity parameter resulting from the modulation of the current phase of each transmitted beam relative to the sum of all the other transmitted beams; and
(d) calculating based on said variations a phase offset of the current phase of each transmitted beam relative to a representative phase of the sum of all the other transmitted beams.

2. The method of claim 1 , further comprising actuating the corresponding adjustable phase modulator of each transmitted beam to perform a phase correction derived from the calculated phase offset.

3. The method of claim 1 , wherein the current phase of each transmitted beam is modulated at a modulation frequency, and wherein said identifying comprises identifying variations in the reflected intensity occurring at more than one harmonic of said modulation frequency.

4. The method of claim 1 , wherein the current phases of a plurality of the transmitted beams are varied simultaneously, the current phase of each of said transmitted beams being modulated at a distinct modulation frequency.

5. The method of claim 1 , wherein the current phase of each transmitted beam is modulated in a manner selected from the group consisting of: a continuous manner over a range of modulation frequencies encompassing said at least three phase states, and a stepped manner between said at least three phase states.

6. The method of claim 1 , wherein the intensity parameter is derived from at least one sensor, sensitive to the transmitted beams, located at the target.

7. The method of claim 1 , wherein the intensity parameter is derived from a detector deployed to sense radiation that is reflected from the target.

8. The method of claim 7 , wherein the detector is located remotely from the target, and wherein the detector is associate with an optical arrangement defining an effective field of view for the detector approximating to an area of the target no greater than a diffraction-limited spot size of the CBC device beams on the target.

9. A coherent beam combination (CBC) system comprising:
(a) an array of beam sources configured to generate a plurality of coherent beams and transmit the plurality of coherent beams towards a target;
(b) a plurality of adjustable phase modulators associated with said array of beam sources so as to allow adjustment of relative phase offsets of said transmitted coherent beams;
(c) a detector deployed for monitoring an intensity parameter that varies as a function of an intensity of radiation of said transmitted coherent beams impinging on an area of the target; and
(d) a controller comprising logic circuitry, said controller being associated with said detector to receive said intensity parameter and with said adjustable phase modulators to control a phase adjustment of said transmitted coherent beams, said controller being configured to:
(i) actuate each of said adjustable phase modulators to modulate a current phase of a corresponding one of said transmitted coherent beams between at least three phase states;
(ii) identify variations in the intensity parameter resulting from the modulation of the current phase of each transmitted coherent beam relative to the sum of all the other transmitted coherent beams; and
(iii) calculate based on said variations a phase offset of the current phase of each transmitted coherent beam relative to a representative phase of the sum of all the other transmitted coherent beams.

10. The system of claim 9 , wherein said controller is further configured to actuate each of said adjustable phase modulators to perform a phase correction derived from the calculated phase offset.

11. The system of claim 9 , wherein said controller is further configured to modulate the current phase of each transmitted beam at a modulation frequency, and to identify variations in the reflected intensity occurring at more than one harmonic of said modulation frequency.

12. The system of claim 9 , wherein said controller is further configured to vary the current phases of a plurality of the transmitted coherent beams simultaneously, the current phase of each of said transmitted coherent beams being modulated at a distinct modulation frequency.

13. The system of claim 9 , wherein said controller is further configured to modulate the current phase of each transmitted coherent beam in a manner selected from the group consisting of: a continuous manner over a range of modulation frequencies encompassing said at least three phase states, and a stepped manner between said at least three phase states.

14. The system of claim 9 , wherein said detector is deployed at the target.

15. The system of claim 9 , wherein said detector is deployed to sense radiation that is reflected from the target.

16. The system of claim 15 , further comprising an optical arrangement associated with the detector and configured to define an effective field of view for the detector approximating to an area of the target no greater than a diffraction-limited spot size of the coherent beams on the target.

17. The method of claim 1 , wherein the representative is an average phase of the sum of all the other transmitted beams.

18. The system of claim 9 , wherein the representative is an average phase of the sum of all the other transmitted beams.

Assignees

• Rafael Advanced Defense Systems Ltd

Inventors

• Golubchik Daniel
• Segev Yehonathan
• Shwa David

Classifications

• H01S3/1307 Primary

  Stabilisation of the phase · CPC title

• H01S3/0085

  Modulating the output, i.e. the laser beam is modulated outside the laser cavity · CPC title

• H01S3/067

  Fibre lasers · CPC title

• H01S3/10053

  Phase control · CPC title

• H01S3/2308

  Amplifier arrangements, e.g. MOPA · CPC title