High-power, phase-locked, laser arrays
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.
1. A method for producing mutually-coherent operation of a plurality of light emitters, each of the emitters outputting a respective power and having a respective 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 to all of the emitters at least a narrowband portion of the composite beam, the portion having a selected wavelength and containing a respective contribution from each of the emitters,
wherein mutually coherent, phase-locked operation of the plurality of emitters is achieved such that each of the emitters lases at the selected wavelength with a phase difference that results in a coherent output beam that constructively combines the beams from each of the emitters such that the output beam has a brightness that is greater than the brightnesses of the individual emitters.
2. The method of claim 1 , wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters lases at a selected wavelength.
3. The method of claim 2 , wherein mutually coherent operation of the plurality of emitters is achieved such that each of the emitters lases at the selected wavelength with a phase difference that results in the output beam having a brightness that is greater than the brightnesses of the individual emitters.
4. 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, phase-locked operation of the plurality of emitters is achieved such that each of the emitters lases at the same wavelength with a phase difference that results in a coherent output beam that constructively combines the beams from each of the emitters such that the output beam has a brightness that is greater than respective brightnesses of the individual emitters.
5. The method of claim 4 , wherein the beams received from the emitters are mixed by overlapping the received beams in the focal plane of the lens.
6. The method of claim 4 , wherein the optical element is a holographic optical element.
7. The method of claim 6 , wherein the Bragg grating is recorded holographically in the optical element.
8. The method of claim 4 , 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.
9. The method of claim 8 , further comprising positioning a collimating lens between the optical element and the front emitting apertures of the emitters.
10. The method of claim 8 , 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.