Apparatus and method for a waveguide with an index profile manifesting a central dip for better energy extraction
First Claim
1. An apparatus comprising:
- an optical device configured to operate in a band of wavelengths corresponding to a gain band of one or more active rare-earth species, wherein the device includes a multimode signal waveguide having a central dip in the refractive index profile, the signal waveguide having a characteristic diameter, the signal waveguide being surrounded by an adjacent pedestal region having an index of refraction that is lower than a peak index of refraction of the signal waveguide, the pedestal region being surrounded by an adjacent inner cladding, wherein the inner cladding has an index of refraction value that is lower than the index of refraction of the pedestal region, the inner cladding being surrounded by an adjacent outer cladding, wherein the index of refraction drops from the value at the inner cladding to a lower value at the outer cladding.
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Abstract
A method and apparatus is described that use an index-of-refraction profile having a significant central dip in refractive index (or another tailored index profile) within the core of a gain fiber or a gain waveguide on a substrate. The benefits of this central dip (more power with a given mode structure) are apparent when an input beam is akin to that of a Gaussian mode. In some embodiments, the invention provides a fiber or a substrate waveguide having an index profile with a central dip, but wherein the device has no doping. Some embodiments use a central dip surrounded by a higher-index ring in the index of refraction of the core of the fiber, while other embodiments use a trench between an intermediate-index central core portion and the ring, or use a plurality of rings and/or trenches. Some embodiments use an absorber in at least one core ring.
57 Citations
34 Claims
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1. An apparatus comprising:
an optical device configured to operate in a band of wavelengths corresponding to a gain band of one or more active rare-earth species, wherein the device includes a multimode signal waveguide having a central dip in the refractive index profile, the signal waveguide having a characteristic diameter, the signal waveguide being surrounded by an adjacent pedestal region having an index of refraction that is lower than a peak index of refraction of the signal waveguide, the pedestal region being surrounded by an adjacent inner cladding, wherein the inner cladding has an index of refraction value that is lower than the index of refraction of the pedestal region, the inner cladding being surrounded by an adjacent outer cladding, wherein the index of refraction drops from the value at the inner cladding to a lower value at the outer cladding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An apparatus comprising:
an optical device configured to operate in a band of wavelengths corresponding to a gain band of one or more active rare-earth species, wherein the device includes a multimode signal waveguide having a central dip in the refractive index profile, the signal waveguide having a characteristic diameter, the signal waveguide being surrounded by an adjacent index pedestal having an index of refraction that is lower than a peak index of refraction of the signal waveguide and higher than an inner cladding region, wherein the inner cladding is adjacent to and surrounding the index pedestal. - View Dependent Claims (22, 23, 24)
- 25. A pulsed fiber amplifier, in which a multimode doped core of a gain fiber contains a central dip in the refractive index profile, the doped core being surrounded by an adjacent pedestal region having an index of refraction that is lower than a peak index of refraction of the doped core, the pedestal region being surrounded by an adjacent inner cladding, wherein the inner cladding has an index of refraction value that is lower than the index of refraction of the pedestal region, the inner cladding being surrounded by an adjacent outer cladding, wherein the index of refraction drops from the value at the inner cladding to a lower value at the outer cladding.
Specification