Wavelength beam combining laser systems utilizing lens roll for chief ray focusing
In various embodiments, a wavelength beam combining laser system includes a fast-axis collimation lens that is rotated with respect to a plurality of emitters in order to converge the emitted beams onto a dispersive element and/or reduce the size of the multi-wavelength output beam of the system.
1. A laser system comprising:
a plurality of beam emitters each emitting an individual beam, each beam having a fast-diverging axis and a slow-diverging axis, the plurality of beam emitters being arranged in an array having a lateral dimension;
disposed optically downstream of the plurality of beam emitters, a fast-axis collimation (FAC) lens (A) for (i) receiving the emitted beams and (ii) collimating the beams along their fast-diverging axes, and (B) having a lateral dimension rotated at a non-zero angle with respect to the lateral dimension of the plurality of beam emitters;
disposed optically downstream of the FAC lens, a beam rotator for (i) rotating the beams and (ii) directing the rotated beams toward a dispersive element;
a dispersive element for receiving and dispersing the rotated beams, wherein (i) the rotation of the FAC lens with respect to the plurality of beam emitters causes the rotated beams to at least partially overlap at the dispersive element, and (ii) no focusing optics for overlapping the beams at the dispersive element are disposed between the plurality of beam emitters and the dispersive element; and
a partially reflective output coupler for receiving the dispersed beams, reflecting a first portion thereof back toward the dispersive element, and transmitting a second portion thereof as a multi-wavelength output beam.
2. The laser system of claim 1 , wherein the beam rotator flips the fast-diverging axis and the slow-diverging axis of each beam.
3. The laser system of claim 1 , wherein the FAC lens is discrete and separate from the beam rotator.
4. The laser system of claim 1 , wherein the FAC lens and the beam rotator are portions of a unitary optical element.
5. The laser system of claim 1 , wherein the beam rotator has a lateral dimension rotated at the non-zero angle with respect to the lateral dimension of the plurality of beam emitters.
6. The laser system of claim 1 , wherein the beam rotator has a lateral dimension rotated at a second non-zero angle with respect to the lateral dimension of the plurality of beam emitters, the second non-zero angle not being equal to the non-zero angle.
7. The laser system of claim 1 , wherein the beam rotator has a lateral dimension that is not rotated with respect to the lateral dimension of the plurality of beam emitters.
8. The laser system of claim 1 , wherein the dispersive element comprises a diffraction grating.
9. A method for configuring a laser system, the method comprising:
providing a plurality of beam emitters each emitting an individual beam, each beam having a fast-diverging axis and a slow-diverging axis, the plurality of beam emitters being arranged in an array having a lateral dimension;
providing a fast-axis collimation (FAC) lens disposed optically downstream of the plurality of beam emitters, the FAC lens (A) for (i) receiving the emitted beams and (ii) collimating the beams along their fast-diverging axes, and (B) having a lateral dimension;
providing a beam rotator disposed optically downstream of the FAC lens, the beam rotator for (i) rotating the beams and (ii) directing the rotated beams toward a dispersive element;
providing a dispersive element for receiving and dispersing the rotated beams;
providing a partially reflective output coupler for receiving the dispersed beams, reflecting a first portion thereof back toward the dispersive element, and transmitting a second portion thereof as a multi-wavelength output beam having a beam size; and
rotating the FAC lens relative to the beam emitters, whereby the lateral dimension of the FAC lens is rotated with respect to the lateral dimension of the plurality of beam emitters, to reduce the beam size of the output beam,
wherein no focusing optics for overlapping the beams at the dispersive element are disposed between the plurality of beam emitters and the dispersive element.
10. The method of claim 9 , wherein the lateral dimension of the FAC lens is rotated with respect to the lateral dimension of the plurality of beam emitters until the beam size is substantially minimized.
11. The method of claim 9 , wherein the rotation of the lateral dimension of the FAC lens with respect to the lateral dimension of the plurality of beam emitters causes the rotated beams to at least partially overlap at the dispersive element.
12. The method of claim 9 , wherein the beam rotator has a lateral dimension, and further comprising rotating the lateral dimension of the beam rotator with respect to the lateral dimension of the plurality of beam emitters.
13. The method of claim 12 , wherein the lateral dimensions of the beam rotator and the FAC lens are rotated by approximately the same angle with respect to the lateral dimension of the plurality of beam emitters.
14. The method of claim 12 , wherein the lateral dimensions of the beam rotator and the FAC lens are rotated substantially simultaneously.
15. The method of claim 9 , wherein the beam rotator flips the fast-diverging axis and the slow-diverging axis of each beam.
16. The method of claim 9 , wherein the FAC lens is discrete and separate from the beam rotator.
17. The method of claim 9 , wherein the FAC lens and the beam rotator are portions of a unitary optical element.
18. The method of claim 9 , wherein the dispersive element comprises a diffraction grating.
19. The method of claim 9 , further comprising coupling the output beam into an optical fiber.
20. The laser system of claim 1 , wherein each of the beam emitters comprises a diode emitter disposed within a diode bar.