High-power, phased-locked, laser arrays

• US 20060171428A1
• Filed: 02/03/2006
• Published: 08/03/2006
• 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 7,949,030 B2
• Time in Patent Office: Days
• US Class Current: 372/9
• 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. A system for producing mutually-coherent operation of a plurality of light emitters, each of the emitters outputting a respective power, the system comprising:

an optical system that mixes respective beams received from each of the plurality of emitters;

a beam-combining element that receives the mixed beams and forms at least one composite beam containing a respective contribution from each of the emitters; and

a wavelength-selective output coupler that receives a single optical path output from the beam-combining element, and feeds back through the beam-combining element to the emitters at least a portion of the light received along the optical path, the portion having a selected wavelength,

wherein coherent operation of all 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.

3. The system of claim 1, wherein the optical system comprises at least one lens that mixes the beams received from the emitters by focusing the received beams onto a focal plane of the lens.

4. The system of claim 3, wherein the lens performs an optical Fourier transform on the beams received from the emitters.

5. The system of claim 3, wherein the beam-combining element is positioned in the focal plane of the lens.

6. The system of claim 1, wherein the beam-combining element is a diffractive optical element.

7. The system of claim 6, wherein the beam-combining element is a digital optical element.

8. The system of claim 6, wherein the beam-combining element is a holographic optical element.

9. The system of claim 8, wherein the holographic optical element comprises a three-dimensional, Bragg grating element having a Bragg grating recorded therein.

10. The system of claim 9, wherein the Bragg grating is a reflective Bragg grating.

11. The system of claim 9, wherein the Bragg grating is a transmissive Bragg grating.

12. The system of claim 5, further comprising a second lens, wherein the beam-combing element is positioned in a focal plane of the second lens.

13. The system of claim 1, further comprising a path selector that allows the at least one composite beam therethrough.

14. The system of claim 1, wherein the output coupler reflects at least a portion of the composite beam back through the path selector.

15. The system of claim 1, wherein the output coupler comprises a three-dimensional Bragg grating element having a holographic Bragg grating recorded therein.

16. The system of claim 1, wherein the output coupler comprises a phase-conjugate mirror.

17. The system of claim 1, wherein the output coupler comprises a diffraction grating.

18. The system of claim 1, wherein the output coupler is a tunable output coupler that provides for wavelength tuning of the reflected portion of the composite beam.

19. The system of claim 18, wherein the tunable output coupler provides for the wavelength tuning via angular adjustment of the output coupler.

2. A system for producing mutually-coherent operation of a plurality of light emitters, the system comprising:

a three-dimensional, Bragg grating element that receives respective light beams emitted from each of the emitters, reflects a respective narrowband portion of each of the received light beams, and feeds back the reflected narrowband portions into the emitters in such a way that narrowband light from each of the emitters is fed back into at least one other emitter of the plurality of emitters.

20. The system of claim 2, wherein the Bragg grating element receives the respective light beams by receiving a composite beam containing a respective contribution from each of the emitters.

21. The system of claim 20, further comprising an optical system that creates the composite beam.

22. The system of claim 21, wherein the optical system that creates the composite beam includes a holographic optical element that receives the beams from the emitters and forms at least one composite beam containing the respective contributions from each of the emitters.

23. The system of claim 2, wherein each of the light emitters outputs its respective light beam from a respective front emitting aperture thereof, and wherein the Bragg grating element is positioned proximate the front-emitting apertures of the light emitters.

24. The system of claim 23, further comprising a collimating lens positioned between the Bragg grating and the front emitting apertures of the light emitters.

25. The system of claim 2, wherein each of the light emitters outputs its respective light beam from a respective front emitting aperture thereof, and wherein a diffraction pattern formed on the front emitting apertures of the light emitters by the reflection from the Bragg grating element at least substantially repeats a spatial arrangement of the light emitters.

26. The system of claim 2, wherein the Bragg grating is a reflective Bragg grating.

27. The system of claim 2, wherein the Bragg grating is a transmissive Bragg grating.

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

a lens that receives a respective emitted beam from each of the laser emitters, performs an optical Fourier transform on the emitted beams, and mixes the transformed beams in a focal plane of the lens;

a diffractive optical element positioned in the focal plane of the lens that forms a composite beam that contains a respective contribution from each of the emitted beams;

a path selector that allows the composite beam to pass therethrough along a selected optical path; and

a three-dimensional, Bragg grating element that receives the composite beam along the selected optical path, and causes 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 multiple emitters.