Spectral beam combined laser system and method

1. A spectral beam combined laser system comprising an optical gain element array, a transform element having a focal plane, a diffraction element and a reflecting element, wherein said optical gain element array, said transform element, said diffraction element, and said reflecting element are sequentially positioned in an optical path, wherein

said optical gain element array comprises a plurality of gain elements that radiate laser beams having different wavelengths;

said transform element is positioned such that the focal plane of the transform element is at a reflecting rear facet of the optical gain element array, and the transform element focuses and spatially overlaps the laser beams received from said optical gain element array at said diffraction element;

said diffraction element is positioned at the focal plane of the transform element and diffracts the laser beams spatially overlapped by the transform element to spectrally combine the laser beams to the reflecting element; and

said reflecting element is positioned to intercept a portion of the laser beams diffracted by the diffraction element and feedback the intercepted laser beams to the optical gain element array in a V-shaped off-axis external cavity with an off-axis reflecting angle, wherein said V-shaped off-axis external cavity with the off-axis reflecting angle is formed between the reflecting element and the optical gain element array such that the laser beams subjected to feedback by the V-shaped off-axis external cavity are output underneath the reflecting element as output laser beams by said diffraction element.

2. The spectral beam combined laser system according to claim 1 , wherein the optical gain element array is selected from the group consisting of a semiconductor laser array and a fiber laser array.

3. The spectral beam combined laser system according to claim 1 , further comprising a wave shaping element positioned after the optical gain element array and before the transform element, for shaping the laser beams radiated from the optical gain element array.

4. The spectral beam combined laser system according to claim 3 , wherein the wave shaping element includes a first shaping unit for shaping the laser beams in a first direction and a second shaping unit for shaping the laser beams in a second direction perpendicular to the first direction.

5. The spectral beam combined laser system according to claim 4 , wherein the wave shaping element includes a third shaping unit for performing beam transformation to the laser beams having been shaped by the first shaping unit and the second shaping unit.

6. The spectral beam combined laser system according to claim 3 , wherein the wave shaping element includes a first shaping unit for shaping the laser beams in a first direction and a third shaping unit for performing beam transformation to the laser beams having been shaped by the first shaping unit.

7. The spectral beam combined laser system according to claim 1 , wherein the diffraction element is selected from the group of consisting of a reflective diffraction grating and a transmission diffraction grating.

8. The spectral beam combined laser system according to claim 1 , wherein the off-axis angle is less than 10°.

9. The spectral beam combined laser system according to claim 8 , wherein the off-axis angle is equal to or more than 1°.

10. A method of generating spectrally combined laser beams by a spectral beam combined laser system, the method comprising:

a) radiating a plurality of laser beams having different wavelength in a V-shaped off-axis external cavity with an off-axis angle, by an optical gain element array;

b) focusing the radiated plurality of laser beams and causing the laser beams being spatially overlapped with each other;

c) diffracting the spatially overlapped laser beams to cause the laser beams being spectrally overlapped;

d) intercepting a portion of the diffracted laser beams to feed back the intercepted laser beams in the V-shaped off-axis external cavity by a reflecting element, wherein the V-shaped off-axis external cavity is formed between the reflecting element and the optical gain element array; and

e) outputting underneath the reflecting element, as output laser beam, the laser beams subjected to feedback in the V-shaped off-axis external cavity.

11. The method according to claim 10 , further comprising a step of shaping the laser beams radiated by the optical gain element array, after step a) and before step b).

12. The method according to claim 11 , wherein the step of shaping the laser beams comprises a step of shaping the laser beams in a first direction and shaping the laser beams in a second direction perpendicular to the first direction.

13. The method according to claim 12 , wherein the step of shaping the laser beams further comprises a step of performing beam transformation to the laser beams having been shaped in the first direction and the second direction.

14. The method according to claim 10 , wherein the step of shaping the laser beams comprises a step of shaping the laser beams in a first direction and performing beam transformation to the laser beams having been shaped in the first direction.

15. The method according to claim 10 , wherein the off-axis angle is less than 10°.

16. The method according to claim 15 , wherein the off-axis angle is equal to or more than 1°.