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.

The present invention provides a spectral beam combined laser system comprising an optical gain element array, a transform element, a diffraction element and a reflecting element, which are sequentially positioned in an optical path, wherein said optical gain element array comprises a plurality of gain elements radiate laser beams having different wavelength; said transform element focuses and spatially overlaps the laser beams received from said optical gain element array at said diffraction element; said diffraction element diffracts the laser beams spatially overlapped by the transform element to the reflecting element; and said reflecting element feeds back a portion of the laser beams to the optical gain element array in a V-shaped off-axis external cavity with off-axis angle, wherein said V-shaped off-axis external cavity is formed between the reflecting element and the optical gain element array.

The present invention provides a spectral beam combined laser system comprising an optical gain element array, a transform element, a diffraction element and a reflecting element, which are sequentially positioned in an optical path, wherein said optical gain element array comprises a plurality of gain elements radiate laser beams having different wavelength; said transform element focuses and spatially overlaps the laser beams received from said optical gain element array at said diffraction element; said diffraction element diffracts the laser beams spatially overlapped by the transform element to the reflecting element; and said reflecting element feeds back a portion of the laser beams to the optical gain element array in a V-shaped off-axis external cavity with off-axis angle, wherein said V-shaped off-axis external cavity is formed between the reflecting element and the optical gain element array.