Wavelength beam combining laser systems utilizing prisms for beam quality improvement and bandwidth reduction

1. A wavelength beam combining laser system comprising:

a beam emitter emitting a plurality of discrete beams;

focusing optics for focusing the plurality of beams toward a diffraction grating;

the diffraction grating for receiving and dispersing the received focused beams, wherein a focal plane of the beams defined by the focusing optics is angled with respect to a plane defined by the diffraction grating;

a partially reflective output coupler positioned to receive the dispersed beams, transmit a portion of the dispersed beams therethrough as a multi-wavelength output beam, and reflect a second portion of the dispersed beams back toward the beam emitter; and

disposed optically downstream of the focusing optics and optically upstream of the diffraction grating, one or more first prisms for (i) receiving the beams on an entrance surface of one of the first prisms at an angle of incidence and (ii) transmitting the beams from an exit surface of one of the first prisms to the diffraction grating at an exit angle smaller than the angle of incidence, whereby (a) the resulting focal plane of the beams is rotated to be substantially coplanar with the plane defined by the diffraction grating and (b) the sizes of the beams incident on the diffraction grating are substantially equal to each other.

2. The laser system of claim 1 , wherein the one or more first prisms consist essentially of a single first prism having the entrance surface and the exit surface.

3. The laser system of claim 1 , wherein the one or more first prisms comprise a plurality of first prisms, the entrance and exit surfaces being on different first prisms.

4. The laser system of claim 1 , wherein the diffraction grating is reflective, whereby the dispersed beams from the diffraction grating are transmitted through at least one of the first prisms before being received by the output coupler.

5. The laser system of claim 1 , wherein the diffraction grating is transmissive.

6. The laser system of claim 1 , further comprising a second prism, disposed optically downstream of the diffraction grating and optically upstream of the output coupler, wherein dispersed beams from the diffraction grating are received by an entrance surface of the second prism at a second angle of incidence and transmitted from an exit surface of the second prism at a second exit angle larger than the second angle of incidence, whereby beam-size expansion introduced by the one or more first prisms is reduced or substantially eliminated.

7. The laser system of claim 1 , further comprising an optical telescope disposed between the diffraction grating and the output coupler.

8. The laser system of claim 7 , wherein the optical telescope comprises two cylindrical lenses having optical power in a wavelength beam combining dimension.

9. A method of wavelength beam combining a plurality of beams having different wavelengths, the method comprising:

focusing the plurality of beams toward a diffraction grating, a focal plane of the beams being angled with respect to a plane defined by the diffraction grating;

rotating the focal plane of the beams such that the focal plane is substantially coplanar with the plane defined by the diffraction grating;

wavelength-dispersing the beams with the diffraction grating;

reflecting a first portion of the dispersed beams back onto the diffraction grating; and

transmitting a second portion of the dispersed beams as a multi-wavelength output beam.

10. The method of claim 9 , wherein the focal plane of the beams is rotated by one or more first prisms disposed optically upstream of the diffraction grating.

11. The method of claim 9 , wherein rotating the focal plane of the beams expands a size of at least one of the beams.

12. The method of claim 11 , further comprising reducing or substantially eliminating the beam-size expansion after the beams have been wavelength-dispersed.

13. The method of claim 12 , wherein the beam-size expansion is reduced or substantially eliminated by one or more second prisms disposed optically downstream of the diffraction grating.

14. The method of claim 9 , wherein wavelength-dispersing the beams comprises transmitting the beams through the diffraction grating.

15. The method of claim 9 , wherein wavelength-dispersing the beams comprises reflecting the beams with the diffraction grating.

16. A wavelength beam combining laser system comprising:

a beam emitter emitting a plurality of discrete beams;

focusing optics for focusing the plurality of beams toward a diffraction grating, the focusing optics defining a focal plane of the beams;

the diffraction grating for receiving and dispersing the received focused beams;

a partially reflective output coupler positioned to receive the dispersed beams, transmit a portion of the dispersed beams therethrough as a multi-wavelength output beam, and reflect a second portion of the dispersed beams back toward the beam emitter; and

disposed optically downstream of the focusing optics and optically upstream of the diffraction grating, a first prism for (i) receiving the beams on an entrance surface of the first prism at an angle of incidence and (ii) transmitting the beams from an exit surface of the first prism to the diffraction grating at an exit angle, whereby (a) the resulting focal plane of the beams is substantially coplanar with the plane defined by the diffraction grating and (b) the sizes of the beams incident on the diffraction grating are substantially equal to each other.

17. The laser system of claim 16 , wherein the diffraction grating is disposed on the exit surface.

18. The laser system of claim 16 , wherein the diffraction grating and the first prism are a single integrated component.

19. The laser system of claim 16 , wherein the diffraction grating is reflective, whereby the dispersed beams from the diffraction grating are transmitted through the first prism before being received by the output coupler.

20. The laser system of claim 16 , wherein the diffraction grating is transmissive.

21. The laser system of claim 16 , further comprising a second prism disposed optically downstream of the diffraction grating and optically upstream of the output coupler.

22. The laser system of claim 21 , wherein dispersed beams from the diffraction grating are received by an entrance surface of the second prism at a second angle of incidence and transmitted from an exit surface of the second prism at a second exit angle larger than the second angle of incidence, whereby a size of at least one of the beams is decreased.

23. The laser system of claim 16 , further comprising an optical telescope disposed between the diffraction grating and the output coupler.

24. The laser system of claim 23 , wherein the optical telescope comprises two cylindrical lenses having optical power in a wavelength beam combining dimension.

25. The laser system of claim 16 , further comprising a second prism disposed optically downstream of the focusing optics and optically upstream of the first prism.

26. The laser system of claim 16 , wherein the focal plane of the beams defined by the focusing optics is angled with respect to the plane defined by the diffraction grating.