HIGH-POWER, PHASE-LOCKED, LASER ARRAYS

• US 20120027035A1
• Filed: 05/23/2011
• Published: 02/02/2012
• Est. Priority Date: 02/03/2005
• Status: Active Grant

• Current Assignee: Necsel Intellectual Property Inc. (Ushio Incorporated)
• Original Assignee: PD-LD Incorporated (Ushio Incorporated)
• Inventors: Volodin, Boris Leonidovich
• Granted Patent: US 8,340,150 B2
• Time in Patent Office: Days
• US Class Current: 372/32
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/065 Mode locking; Mode suppression; Mode selection ; Self pulsating
• CPC Class Codes: H01S 5/0654 Single longitudinal mode emission
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/148 using a Talbot cavity
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4062 with an external cavity or using internal filters, e.g. Talbot filters
• CPC Class Codes: H01S 5/4068 with lateral coupling by axially offset or by merging waveguides, e.g. Y-couplers

Abstract

High-power, phased-locked, laser arrays as disclosed herein utilize a system of optical elements that may be external to the laser oscillator array. Such an external optical system may achieve mutually coherent operation of all the emitters in a laser array, and coherent combination of the output of all the lasers in the array into a single beam. Such an “external gain harness” system may include: an optical lens/mirror system that mixes the output of all the emitters in the array; a holographic optical element that combines the output of all the lasers in the array, and an output coupler that selects a single path for the combined output and also selects a common operating frequency for all the coupled gain regions.

Claims

1-2. -2. (canceled)

3. A method for producing mutually-coherent operation of a plurality of light emitters, each of the emitters outputting a respective power, the method comprising:

combining respective beams received from each of the plurality of emitters to form a composite beam containing a respective contribution from each of the emitters; and

feeding back to all of the emitters at least a portion of the composite beam, the portion having a selected wavelength and containing a respective contribution from each of the emitters,

wherein mutually coherent operation of all of the emitters is achieved with a phase difference that results in a coherent output beam from the system that effectively combines the powers from each of the emitters.

4. The method of claim 3, wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters laser at a selected wavelength.

5. The method of claim 4, wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters laser at the selected wavelength with a phase difference that results in the coherent output beam from the system.

6. The method of claim 3, wherein each of the emitters outputs a respective power and brightness, and

wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters laser at the selected wavelength with a phase difference that results in the coherent output beam effectively combining the powers from each of the emitters such that the output beam has a brightness that is greater than the brightnesses of the individual emitters.

7. A method for producing mutually-coherent operation of a plurality of laser emitters, the method comprising:

receiving a respective emitted beam from each of the emitters, performing an optical Fourier transform on the emitted beams, and mixing the transformed beams in a focal plane of a lens;

positioning in the focal plane of the lens a diffractive, three-dimensional optical element that forms a composite beam that contains a respective contribution from each of the emitted beams, the diffractive optical element having a Bragg grating formed therein;

allowing the composite beam to pass through a path selector along a selected optical path; and

causing at least a portion of the composite beam to be reflected back along the optical path through the path selector, such that the reflected portion is fed back through the diffractive optical element and the lens into the emitters in such a way that narrowband light from each of the emitters is fed back into all of the emitters, and

wherein mutually coherent operation of all the emitters is achieved such that each of the emitters laser at the same wavelength.

8. The method of claim 7, wherein the beams received from the emitters are mixed by overlapping the received beams in the focal plane of the lens.

9. The method of claim 7, wherein the optical element is a holographic optical element.

10. The method of claim 9, wherein the Bragg grating is recorded holographically in the optical element.

11. The method of claim 7, wherein each of the emitters outputs its respective beam from a respective front emitting aperture, the method further comprising positioning the optical element proximate the front-emitting apertures of the emitters.

12. The method of claim 11, further comprising positioning a collimating lens between the optical element and the front emitting apertures of the emitters.

13. The method of claim 11, further comprising forming a diffraction pattern on the front emitting apertures of the emitters, by reflection from the three-dimensional optical element, that repeats a spatial arrangement of the emitters.

14. A method for producing mutually-coherent operation of a plurality of light emitters, each of the emitters outputting a respective power and brightness, the method comprising:

combining respective beams received from each of the plurality of emitters to form a composite beam containing a respective contribution from each of the emitters; and

feeding back through a beam-combining element at least a portion of the light containing the respective contribution from each of the emitters, the portion having a selected wavelength,

wherein the portion is fed back into the emitters in such a way that each of the emitters receives narrowband light from every other emitter, and

wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters laser at the selected wavelength with a phase difference that results in a coherent output beam from the system that effectively combines the powers from each of the emitters such that the output beam has a brightness that is greater than the brightnesses of the individual emitters.

15. The method of claim 14, wherein the beams received from the emitters are mixed by overlapping the received beams in a focal plane of a lens.

16. The method of claim 15, wherein the lens performs an optical Fourier transform on the beams received from the emitters.

17. The method of claim 15, wherein the beam-combining element is positioned in the focal plane of the lens.

18. The method of claim 14, wherein the beam-combining element is a diffractive optical element.

19. The method of claim 18, wherein the beam-combining element is a digital optical element.

20. The method of claim 14, wherein the beam-combining element is a three-dimensional optical element having a Bragg grating recorded holographically therein.

21. The method of claim 20, wherein the Bragg grating is a reflective Bragg grating.

22. The method of claim 20, wherein the Bragg grating is a transmissive Bragg grating.