Laser system with staircased slow-axis collimators
In various embodiments, pointing errors in a non-wavelength-beam-combining dimension of a laser system are at least partially alleviated via staircased collimation lenses.
1. A laser system comprising:
a plurality of beam emitters each emitting one or more beams;
a dispersive element for receiving the beams and combining the beams, in a wavelength-beam-combining (WBC) dimension, into a multi-wavelength beam;
a plurality of collimators disposed optically downstream of the beam emitters and optically upstream of the dispersive element, wherein each collimator receives the one or more beams from a beam emitter and collimates the one or more beams in a non-WBC dimension; and
a partially reflective output coupler for receiving the multi-wavelength beam from the dispersive element, transmitting a first portion of the multi-wavelength beam as an output beam, and reflecting a second portion of the multi-wavelength beam back toward the dispersive element,
wherein:
the dispersive element is tilted, in the non-WBC dimension, at a non-zero angle such that first-order reflections of the beams from the dispersive element are directed away from the beam emitters, whereby pointing error is introduced into the multi-wavelength beam, and
optical axes of two or more of the collimators are displaced from each other in the non-WBC dimension, whereby the pointing error arising from the tilted dispersive element is reduced.
2. The laser system of claim 1 , wherein the non-WBC dimension corresponds to a slow axis of the beams.
3. The laser system of claim 1 , wherein the non-WBC dimension corresponds to a fast axis of the beams.
4. The laser system of claim 1 , wherein the dispersive element comprises a diffraction grating.
5. The laser system of claim 1 , wherein at least one of the beam emitters comprises a diode bar configured to emit a plurality of discrete beams.
6. The laser system of claim 1 , wherein the collimators introduce beam smear in the non-WBC dimension at the dispersive element.
7. The laser system of claim 1 , further comprising, associated with each beam emitter, (i) a second collimator, and (ii) an optical rotator for rotating the one or more beams approximately 90°.
8. The laser system of claim 7 , wherein each collimator is a slow-axis collimator and each second collimator is a fast-axis collimator.
9. The laser system of claim 1 , wherein an optical distance between each of the collimators and the dispersive element is approximately equal.
10. The laser system of claim 1 , wherein heights of two or more of the collimators are different.
11. The laser system of claim 1 , wherein heights of two or more of the collimators are approximately equal.
12. The laser system of claim 1 , wherein heights of all of the collimators are approximately equal.
13. The laser system of claim 1 , further comprising one or more folding mirrors disposed optically downstream of the dispersive element and optically upstream of the output coupler.
14. A method of aligning a laser system comprising (i) a plurality of beam emitters each configured to emit one or more beams, (ii) a dispersive element for receiving the beams and combining the beams, in a wavelength-beam-combining (WBC) dimension, into a multi-wavelength beam, and (iii) a partially reflective output coupler for receiving the multi-wavelength beam from the dispersive element, transmitting a first portion of the multi-wavelength beam as an output beam, and reflecting a second portion of the multi-wavelength beam back toward the dispersive element, the method comprising:
combining beams emitted by the plurality of beam emitters into the multi-wavelength beam at the dispersive element;
preventing first-order reflections from the dispersive element from propagating back to the plurality of beam emitters; and
reducing pointing error of the multi-wavelength beam.
15. The method of claim 14 , wherein preventing the first-order reflections from the dispersive element from propagating back to the plurality of beam emitters comprises tilting the dispersive element at a non-zero angle in the non-WBC dimension.
16. The method of claim 14 , wherein the pointing error is reduced by displacing optical axes of two or more collimators from each other in the non-WBC dimension, the two or more collimators being disposed optically downstream of the beam emitters and optically upstream of the dispersive element.
17. The method of claim 16 , wherein the two or more collimators are slow-axis collimators.
18. The method of claim 16 , wherein the two or more collimators are fast-axis collimators.
19. The method of claim 14 , wherein the non-WBC dimension corresponds to a slow axis of the beams.
20. The method of claim 14 , wherein the non-WBC dimension corresponds to a fast axis of the beams.
21. The method of claim 14 , further comprising rotating the beams approximately 90° before combining the beams into the multi-wavelength beam.
22. A method of aligning a laser system comprising (i) a plurality of beam emitters each configured to emit one or more beams, (ii) a dispersive element for receiving the beams and combining the beams, in a wavelength-beam-combining (WBC) dimension, into a multi-wavelength beam, and (iii) a partially reflective output coupler for receiving the multi-wavelength beam from the dispersive element, transmitting a first portion of the multi-wavelength beam as an output beam, and reflecting a second portion of the multi-wavelength beam back toward the dispersive element, the method comprising:
combining beams emitted by the plurality of beam emitters into the multi-wavelength beam at the dispersive element;
introducing pointing error into the multi-wavelength beam in a non-WBC dimension;
introducing beam smear at the dispersive element in the non-WBC dimension to reduce the pointing error of the multi-wavelength beam; and
reducing the beam smear without increasing the pointing error of the multi-wavelength beam.
23. The method of claim 22 , wherein the pointing error is introduced into the multi-wavelength beam by tilting the dispersive element at a non-zero angle in the non-WBC dimension.
24. The method of claim 22 , wherein the beam smear is introduced by tilting one or more interleaver mirrors at a non-zero angle in the non-WBC dimension, the one or more interleaver mirrors being disposed optically downstream of the beam emitters and optically upstream of the dispersive element.
25. The method of claim 22 , wherein the beam smear is reduced by displacing optical axes of two or more collimators from each other in the non-WBC dimension, the two or more collimators being disposed optically downstream of the beam emitters and optically upstream of the dispersive element.
26. The method of claim 25 , wherein the two or more collimators are slow-axis collimators.
27. The method of claim 25 , wherein the two or more collimators are fast-axis collimators.
28. The method of claim 22 , wherein the non-WBC dimension corresponds to a slow axis of the beams.
29. The method of claim 22 , wherein the non-WBC dimension corresponds to a fast axis of the beams.
30. The method of claim 22 , further comprising rotating the beams approximately 90° before combining the beams into the multi-wavelength beam.