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. An optical fiber configured to propagate at least one lower order mode having a wavelength, λ, said optical fiber comprising:
a core region having a core width; and
a cladding region surrounding said core region, said cladding region comprising a plurality of cladding features disposed in a matrix material, said plurality of cladding features having a maximum feature size, d, said plurality of cladding features separated by bridges having a maximum bridge width, a, said bridge comprising matrix material,
wherein said core width is greater than about 25 micrometers,
wherein said plurality of cladding features are arranged in no more than two layers around said core region, and
wherein said maximum bridge width has a value that yields a ratio of a/λ that is at least about 5.
2. The optical fiber of claim 1 , wherein said maximum bridge width, a, has a value that yields a ratio of a/λ that is less than about 100.
3. The optical fiber of claim 1 , wherein said core width is less than about 300 micrometers.
4. The optical fiber of claim 1 , wherein said maximum feature size, d, has a value that yields a ratio of d/λ that is in a range from about 5 to 100.
5. The optical fiber of claim 1 , wherein said plurality of cladding features have an average center-to-center spacing, Λ, and wherein d/Λ is greater than about 0.4 and less than about 0.9.
6. The optical fiber of claim 1 , wherein said plurality of cladding features are arranged in no more than one layer around said core region.
7. The optical fiber of claim 1 , wherein said plurality of cladding features has two dimensional asymmetries that provide birefringence.
8. The optical fiber of claim 1 , wherein said core region is doped with one or more dopants to provide optical gain.
9. The optical fiber of claim 8 , wherein at least one dopant comprises a rare earth ion.
10. The optical fiber of claim 1 , further comprising an outer cladding region surrounding said cladding region.
11. The optical fiber of claim 1 , wherein said plurality of cladding features comprise material having a refractive index less than a refractive index of said matrix material.
12. An optical system for generating high power solitons, the optical system comprising the optical fiber of claim 1 .
13. A laser system comprising:
the optical fiber of claim 1 , wherein said optical fiber is doped with at least one dopant that provides said optical fiber with optical gain;
an optical cavity formed by reflective elements, said optical fiber included in said optical cavity and optically coupled to said reflective elements; and
an optical pump source optically coupled to said optical fiber and configured to provide pump light to the optical fiber.
14. The laser system of claim 13 , wherein at least one of said reflective elements comprises an optical fiber Bragg grating.
15. The laser system of claim 13 , further comprising a fast optical switch included in said optical cavity.
16. An optical amplification system comprising:
the optical fiber of claim 1 , wherein said optical fiber is doped with a dopant to provide optical gain; and
an optical pump source optically coupled to said optical fiber and configured to provide pump light to the optical fiber.
17. The optical amplification system of claim 16 , wherein the 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.
18. The optical amplification system of claim 16 , further comprising a frequency conversion element.
19. The optical amplification system of claim 16 , wherein said core width is in a range from about 25 micrometers to about 100 micrometers.
20. A chirped pulse amplification system comprising:
the optical amplification system of claim 16 ; and
a pulse compressor.
21. An optical rod for propagating at least one lower order mode having a wavelength, λ, while limiting propagation of higher order modes having a 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 rod comprising:
a first cladding region comprising one or more cladding features; and
a core region surrounded by the said first cladding region, said cladding features configured to substantially confine propagation of said lower order modes to said core region, said core region having a width of at least about 20 micrometers.
22. The optical rod of claim 21 , wherein said width of said core region is at least about 40 micrometers across.
23. The optical rod of claim 21 , wherein said one or more cladding features have a minimum feature size, d, yielding a ratio of d/λ that is at least about 10.
24. The optical rod of claim 21 , wherein said core region and said cladding region are in a substantially optically transmissive main body of said optical rod, said main body comprising material substantially optically transmissive of said wavelength, λ, said main body having a width and thickness at least about 250 μm so as to reduce mode coupling of said at least one lower order mode to said higher order modes.
25. The optical rod of claim 1 , wherein said core region is doped with one or more dopants to provide optical gain.