High-power all fiber telescope

1. An optical fiber device comprising:

an optical waveguide to guide a laser output from a first end of the optical waveguide to a second end of the optical waveguide;

a fiber telescope optically coupled to the second end of the optical waveguide to modify the laser output, the fiber telescope comprising:

a first graded-index optical fiber having a first core radius, a first facet of the first graded-index optical fiber being fused to the second end of the optical waveguide; and

a second graded-index optical fiber having a second core radius that is different from the first core radius, a first facet of the second graded-index optical fiber being fused to a second facet of the first graded-index optical fiber; and

an endcap to receive and reduce a power density of the modified laser output, the endcap being formed of glass, having an endcap radius larger than a fiber telescope radius of the fiber telescope, and being fused to a second facet of the second graded-index optical fiber.

2. The optical fiber device of claim 1 , wherein a total length of the first graded-index optical fiber and the second graded-index optical fiber is greater than one-quarter pitch.

3. The optical fiber device of claim 1 , wherein the first graded-index optical fiber and the second graded-index optical fiber have approximately parabolic refractive-index profiles.

4. The optical fiber device of claim 1 , wherein the first graded-index optical fiber and the second graded-index optical fiber comprise quarter-pitch graded-index lenses.

5. The optical fiber device of claim 1 , wherein the laser output is provided by a single module laser.

6. The optical fiber device of claim 1 , wherein the fiber telescope is to de-magnify the laser output in order to decrease a spot size and increase a numerical aperture at an exit facet of the optical fiber device.

7. The optical fiber device of claim 1 , wherein focal lengths of the first graded-index optical fiber and the second graded-index optical fiber are selected to cause a numerical aperture (NA) of a single module laser to match an NA of an engine including a plurality of laser modules.

8. The optical fiber device of claim 1 , wherein the laser output is provided by an engine including a plurality of fiber laser modules.

9. The optical fiber device of claim 1 , wherein the fiber telescope is to magnify the laser output in order to increase a spot size and decrease a numerical aperture at an exit facet of the optical fiber device.

10. The optical fiber device of claim 1 , wherein focal lengths of the first graded-index optical fiber and the second graded-index optical fiber are selected to cause a numerical aperture (NA) of an engine including a plurality of laser modules to match an NA of a single laser module.

11. The optical fiber device of claim 1 , wherein at least one of the first graded-index optical fiber and the second graded-index optical fiber is a non-quarter pitch graded-index lens.

12. The optical fiber device of claim 11 , wherein the first graded-index optical fiber and the second graded-index optical fiber have a same diameter and a same graded-index profile and are formed of a monolithic piece of graded-index material.

13. The optical fiber device of claim 1 , wherein the fiber telescope is configured to cause a shift of an image plane relative to a caustic waist of the laser output in association with achieving imperfect imaging.

14. The optical fiber device of claim 1 , wherein focal lengths of the first graded-index optical fiber and the second graded-index optical fiber are selected to achieve a particular divergence of the laser output.

15. The optical fiber device of claim 1 , wherein the fiber telescope is to modify the laser output by causing at least one of:

a magnification of the laser output,

a demagnification of the laser output,

a shifting of an image plane relative to a caustic waist of the laser output, or

beam shaping of the laser output.

16. An optical fiber device comprising:

an optical waveguide to guide a laser output from a first end of the optical waveguide to a second end of the optical waveguide;

a fiber telescope optically coupled to the second end of the optical waveguide to modify the laser output,

wherein the fiber telescope comprises at least one graded-index optical fiber having a core,

wherein a total length of the at least one graded-index optical fiber is greater than one-quarter pitch, and

wherein a facet of the at least one graded-index optical fiber is fused to the second end of the optical waveguide; and

an endcap to receive and reduce a power density of the modified laser output, the endcap being formed of glass, having an endcap radius larger than a fiber telescope radius of the fiber telescope, and being fused to another facet of the at least one graded-index optical fiber.

17. The optical fiber device of claim 16 , wherein the at least one graded-index optical fiber includes a first graded-index optical fiber and a second graded-index optical fiber,

wherein a first facet of the first graded-index optical fiber is the facet that is fused to the second end of the optical waveguide, and

wherein a first facet of the second graded-index optical fiber is fused to a second facet of the first graded-index optical fiber.

18. The optical fiber device of claim 17 , wherein a length of at least one of the first graded-index optical fiber or the second graded-index optical fiber is one-quarter pitch.

19. The optical fiber device of claim 17 , wherein a length of at least one of the first graded-index optical fiber or the second graded-index optical fiber is greater than or less than on one-quarter pitch.

20. The optical fiber device of claim 16 , wherein the at least one graded-index optical fiber includes at least three graded-index optical fibers.

21. The optical fiber device of claim 16 , wherein the at least one graded-index optical fiber includes a graded-index element in which a graded-index profile varies as a function of position along a fiber axis.