Single mode propagation in fibers and rods with large leakage channels
Various embodiments include large cores fibers that can propagate few modes or a single mode while introducing loss to higher order modes. Some of these fibers are holey fibers that comprising cladding features such as air-holes. Additional embodiments described herein include holey rods. The rods and fibers may be used in many optical systems including optical amplification systems, lasers, short pulse generators, Q-switched lasers, etc. and may be used for example for micromachining.
1. A polarization-maintaining (PM) optical fiber for propagating at least one lower order mode having a wavelength, λ, while limiting propagation of higher order modes having said wavelength, λ, by providing said higher order modes with a higher loss than said at least one lower order mode at said wavelength, λ, said optical fiber comprising:
a first cladding region comprising a plurality of cladding features; and
a core region at least partially surrounded by said first cladding region and defined by said plurality of cladding features, said core region having a width of at least about 20 micrometers, said plurality of cladding features configured to substantially confine propagation of said at least one lower order mode to said core region,
wherein said plurality of cladding features are arranged in layers around said core region, and
wherein said core region, said first cladding region, or both said core region and said first cladding region have a two dimensional asymmetry that provides birefringence.
2. The PM optical fiber of claim 1 , wherein said width of said core region is less than about 300 micrometers.
3. The PM optical fiber of claim 1 , wherein said plurality of cladding features are arranged in no more than one layer around said core region.
4. The PM optical fiber of claim 1 , wherein said PM optical fiber comprises at least one stress-producing region.
5. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise stress elements.
6. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise ellipses.
7. The PM optical fiber of claim 1 , wherein said core region is elliptical or rectangular.
8. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise features having different sizes.
9. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise features having an asymmetrical distribution.
10. The PM optical fiber of claim 1 , wherein said core region comprises stress elements.
11. PM optical fiber of claim 1 , wherein at least a portion of said PM optical fiber is coiled.
12. The PM optical fiber of claim 1 , comprising a birefringent crystalline material.
13. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise two or more cladding features having a maximum feature size, d, and an average center-to-center spacing, Λ, and wherein d/Λ is greater than about 0.4 and less than about 0.9.
14. The PM optical fiber of claim 1 , wherein said plurality of cladding features have a maximum feature size, d, that yields a ratio of d/λ, that is in a range from about 5 to 100.
15. The PM optical fiber of claim 1 , wherein said plurality of cladding features comprise two or more cladding features disposed in a matrix material and separated by bridges having a maximum bridge width, a, said bridge comprising matrix material, wherein a/λ is in a range from about 5 to 100.
16. The PM optical fiber of claim 1 , wherein said PM optical fiber is configured to provide a loss for said higher order modes of at least about 0.5 dB.
17. The PM optical fiber of claim 1 , wherein said plurality of cladding features are disposed in a matrix material, and at least one of said plurality of cladding features comprises material having a refractive index less than a refractive index of said matrix material.
18. The PM optical fiber of claim 1 , further comprising a second cladding region surrounding said first cladding region.
19. The PM optical fiber of claim 1 , further comprising a pump guide surrounding said first cladding region and a pump cladding surrounding said pump guide.
20. The PM optical fiber of claim 19 , further comprising an outer layer surrounding said pump cladding.
21. The PM optical fiber of claim 1 , wherein said core region is doped with one or more dopants to provide optical gain.
22. The PM optical fiber of claim 21 , wherein at least one dopant comprises a rare earth ion.
23. A laser system comprising:
an optical cavity formed by reflective elements, said optical cavity comprising:
the PM optical fiber of claim 1 ;
a gain medium doped with at least one dopant; and
an optical pump source configured to provide pump light to said gain medium.
24. The laser system of claim 23 , wherein said PM optical fiber comprises said gain medium.
25. The laser system of claim 23 , wherein at least one of said reflective elements comprises an optical fiber Bragg grating.
26. The laser system of claim 23 , further comprising a fast optical switch included in said optical cavity.
27. An optical amplification system comprising:
the PM optical fiber of claim 1 ;
a gain medium; and
an optical pump source optically coupled to said gain medium and configured to provide pump light to the gain medium.
28. The optical amplification system of claim 27 , wherein said PM optical fiber comprises said gain medium.
29. The optical amplification system of claim 27 , wherein the PM optical fiber comprises a pump guide disposed around said core region and said plurality of cladding features, said pump guide arranged to receive said pump light from said optical pump source.
30. The optical amplification system of claim 27 , further comprising a frequency conversion element.
31. A chirped pulse amplification system comprising:
the optical amplification system of claim 27 ; and
a pulse compressor.
32. The PM optical fiber of claim 1 , wherein said plurality of cladding features are arranged in no more than two layers around said core region.