Optical cross-coupling mitigation systems for wavelength beam combining laser systems
In various embodiments, wavelength beam combining laser systems incorporate optical cross-coupling mitigation systems and/or engineered partially reflective output couplers in order to reduce or substantially eliminate unwanted back-reflection of stray light.
1. A laser system comprising:
an array of beam emitters each emitting a beam having a different wavelength;
focusing optics for focusing the beams toward a dispersive element;
a dispersive element for receiving and dispersing the focused beams, thereby forming a multi-wavelength beam; and
an output coupler comprising (i) a beam-receiving portion for receiving the multi-wavelength beam, reflecting a first portion thereof back to the array of beam emitters via the dispersive element, and transmitting a second portion thereof as an output beam composed of multiple wavelengths, and (ii) a non-reflective portion.
2. The laser system of claim 1 , wherein the beam-receiving portion of the output coupler is at least as large as a diameter of the multi-wavelength beam.
3. The laser system of claim 1 , wherein the beam-receiving portion of the output coupler protrudes above the non-reflective portion.
4. The laser system of claim 1 , wherein the non-reflective portion at least partially surrounds the beam-receiving portion.
5. The laser system of claim 1 , wherein a reflectivity to the multi-wavelength beam of the non-reflective portion is less than 1%.
6. The laser system of claim 1 , wherein a reflectivity to the multi-wavelength beam of the beam-receiving portion is less than approximately 15%.
7. The laser system of claim 1 , wherein a reflectivity to the multi-wavelength beam of the beam-receiving portion ranges from approximately 2% to approximately 10%.
8. The laser system of claim 1 , further comprising a non-reflective coating disposed over the non-reflective portion of the output coupler.
9. The laser system of claim 1 , further comprising an end cap over the beam-receiving portion of the output coupler.
10. The laser system of claim 1 , further comprising an optical fiber positioned to receive the output beam.
11. The laser system of claim 1 , further comprising a workpiece positioned to receive the output beam.
12. The laser system of claim 1 , further comprising an optical element for focusing the multi-wavelength beam toward the output coupler.
13. The laser system of claim 12 , wherein the optical element comprises at least one of a cylindrical lens or a spherical lens.
14. The laser system of claim 1 , further comprising a cross-coupling mitigation system for receiving and transmitting the multi-wavelength beam while reducing cross-coupling thereof.
15. The laser system of claim 14 , wherein the beam-receiving portion of the output coupler is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the cross-coupling mitigation system.
16. The laser system of claim 14 , wherein at least a portion of the cross-coupling mitigation system is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the dispersive element.
17. The laser system of claim 14 , wherein the cross-coupling mitigation system comprises an afocal telescope.
18. The laser system of claim 14 , wherein the cross-coupling mitigation system comprises a first optical element having a first focal length and a second optical element having a second focal length, the first optical element being disposed optically upstream of the second optical element.
19. The laser system of claim 18 , wherein the first focal length is at least two times greater than the second focal length.
20. The laser system of claim 18 , wherein the first focal length is at least seven times greater than the second focal length.
21. The laser system of claim 18 , wherein each of the first and second optical elements comprises a lens.
22. The laser system of claim 18 , wherein the first optical element is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the dispersive element.
23. The laser system of claim 18 , wherein the beam-receiving portion of the output coupler is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the second optical element.
24. The laser system of claim 18 , wherein an optical distance between the first and second optical elements is approximately equal to a sum of the first and second focal lengths.