Optical alignment systems and methods for wavelength beam combining laser systems
In various embodiments, wavelength beam combining laser systems incorporate fast-axis collimation lenses and slow-axis collimation lenses (either separately or as portions of a single hybrid lens) optically upstream of an optical rotation system to thereby reduce or minimize cross-talk in the combined output beam.
1. A laser apparatus comprising:
an array of beam emitters each emitting a beam of a different wavelength, each emitted beam having a fast diverging axis and a slow diverging axis;
a hybrid lens disposed optically downstream of the array of beam emitters, the hybrid lens having (i) a first surface for collimating the beams along the fast diverging axis, and (ii) a second surface for reducing divergence of the beams along the slow diverging axis;
disposed optically downstream of the hybrid lens, an optical rotator for rotating the beams;
disposed optically downstream of the optical rotator, focusing optics for focusing the rotated beams toward a dispersive element;
disposed optically downstream of the focusing optics, the dispersive element for receiving and dispersing the focused beams; and
disposed optically downstream of the dispersive element, 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 apparatus of claim 1 , wherein a distance between the hybrid lens and the array of beam emitters is selected to incompletely collimate the beams along the slow diverging axis and thereby introduce cross-talk between the fast diverging axis and slow diverging axis of each of the beams.
3. The laser apparatus of claim 1 , wherein the hybrid lens comprises a fast-axis collimating lens optically bonded, at an interface, to one or more slow-axis collimating lenses.
4. The laser apparatus of claim 3 , wherein at least one of the slow-axis collimating lenses comprises a cylindrical Fresnel lens.
5. The laser apparatus of claim 1 , wherein the hybrid lens comprises a fast-axis collimating lens optically bonded, at an interface, to a plurality of slow-axis collimating lenses.
6. The laser apparatus of claim 5 , wherein at least one of the slow-axis collimating lenses comprises a cylindrical Fresnel lens.
7. The laser apparatus of claim 1 , wherein the hybrid lens consists essentially of a unitary optical component having shaped first and second surfaces.
8. The laser apparatus of claim 1 , wherein the second surface of the hybrid lens is shaped as a plurality of cylindrical Fresnel lenses.
9. The laser apparatus of claim 8 , wherein a spacing of the cylindrical Fresnel lenses is substantially equal to a spacing of the array of beam emitters.
10. The laser apparatus of claim 1 , wherein the dispersive element comprises a diffraction grating.
11. The laser apparatus of claim 1 , wherein the focusing optics comprises at least one of a cylindrical lens or a cylindrical mirror.
12. The laser apparatus of claim 1 , wherein the optical rotator comprises two spaced-apart cylindrical lenses.
13. The laser apparatus of claim 12 , wherein a spacing between the two spaced-apart cylindrical lenses is less than approximately 2 mm.
14. The laser apparatus of claim 1 , wherein an index of refraction of the optical rotator is greater than approximately 1.5.
15. The laser apparatus of claim 1 , wherein a focal length of the optical rotator is less than approximately 2 mm.
16. The laser apparatus of claim 1 , further comprising an optical fiber into which the multi-wavelength output beam is coupled.
17. The laser apparatus of claim 1 , wherein the array of beam emitters comprises a diode bar, each of the beam emitters comprising a diode emitter within the diode bar.
18. The laser apparatus of claim 1 , wherein the first surface is disposed optically downstream of the second surface.
19. The laser apparatus of claim 1 , wherein the second surface is disposed optically downstream of the first surface.