Anti-Stokes-fluorescence-cooled fiber-based gain element

Patent metadata

Field	Value
Publication number	US-10790633-B2
Application number	US-201916541015-A
Country	US
Kind code	B2
Filing date	Aug 14, 2019
Priority date	Aug 15, 2018
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

Fiber-based gain elements, such as fiber lasers, fiber amplifiers, and the like, that have higher power and better frequency stability than can be achieved in the prior art are presented. Embodiments include a fiber-based gain element having a first portion in which anti-Stokes fluorescence (ASF) reduces its temperature below that of an ambient environment and a second portion whose temperature is not reduced below that of the ambient environment, which are thermally coupled so heat can flow from the second portion into the first portion, thereby reducing the average temperature of the gain element. In some embodiments, a core configured to provide optical gain is thermally coupled with a first cladding configured to exhibit ASF cooling via an intervening cladding layer that acts to confine a first pump signal to the core.

First claim

What is claimed is:

1. A fiber-based gain element comprising an optical fiber having a longitudinal axis, a first portion having a first outer surface, and a second portion having a second outer surface, the optical fiber including:
a core configured to provide optical gain in response to a first pump signal; and
a first cladding that surrounds at least a portion of the core, the first cladding configured to exhibit anti-Stokes fluorescence (ASF) in response to a second pump signal, wherein the ASF removes heat from the first cladding;
wherein the optical fiber is arranged such that the first outer surface and the second outer surface are thermally coupled; and
wherein, when the core receives the first pump signal and the first cladding receives the second pump signal:
(i) the first cladding and core are a thermally coupled such that heat flows from the core into the first cladding;
(ii) the first portion has a temperature that is lower than a first temperature and a second portion having a temperature that is higher than the first temperature; and
(iii) heat flows from the second portion to the first portion through the first and second surfaces along a direction that is unaligned with the longitudinal axis.

2. The element of claim 1 wherein the core comprises a first active dopant and the first cladding comprises a second active dopant.

3. The element of claim 2 wherein the first and second active dopants are the same active dopant.

4. The element of claim 1 further comprising second cladding that surrounds at least a portion of the core, the second cladding being between the core and the first cladding, wherein the core has a first refractive index, the first cladding has a second refractive index, and the second cladding has a third refractive index that is lower than the first refractive index and higher than the second refractive index.

5. The element of claim 4 further comprising a third cladding that surrounds at least a portion of the first cladding, the first cladding being between the third cladding and the second cladding, wherein the third cladding has a fourth refractive index that is lower than the second refractive index.

6. The element of claim 1 wherein the optical fiber is arranged in a first arrangement in which the first portion includes a first winding and the second portion includes a second winding, the first winding and second winding being adjacent and thermally coupled through the first and second outer surfaces.

7. The element of claim 1 wherein the first portion includes a plurality of first windings and the second portion includes a plurality of second windings, and wherein the first and second windings are arranged in a close-packed arrangement in which each second winding of the plurality thereof is thermally coupled with at least one first winding of the plurality thereof.

8. The element of claim 1 further comprising a first material that is thermally conductive, wherein the first material is thermally coupled with each of the first outer surface and the second outer surface.

9. The element of claim 1 further comprising the first pump and the second pump, and wherein the fiber-based gain element, first pump, and second pump collectively define an element selected from the group consisting of a fiber laser, a fiber amplifier, and a fiber laser/amplifier combination.

10. The element of claim 1 wherein at least one of the core and the first cladding comprises a host material that is a fluoride glass selected from the group consisting of zirconium barium lanthanum aluminum sodium fluoride (ZBLAN) and zirconium barium lanthanum aluminum sodium lead fluoride (ZBLANP).

11. The element of claim 1 wherein the first pump signal and second pump signal are the same pump signal.

12. A method comprising:
providing a fiber-based gain element comprising an optical fiber having a longitudinal axis, the optical fiber including a first portion having a first outer surface and a second portion having a second outer surface, the optical fiber comprising:
(i) a core that is configured to provide optical gain in response to a first pump signal; and
(ii) a first cladding that is configured to exhibit anti-Stokes fluorescence (ASF) in response to a second pump signal, wherein the first cladding is configured such that the ASF removes heat from the first cladding;
wherein the first cladding and core are thermally coupled such that heat flows from the core into the first cladding when the core receives the first pump signal and the first cladding receives the second pump signal;

arranging the optical fiber in a first arrangement in which the first outer surface and second outer surface are thermally coupled and heat flows between the first portion and second portion through the first and second outer surfaces along a direction that is unaligned with the longitudinal axis when the core receives the first pump signal and the first cladding receives the second pump signal;
optically coupling the first pump signal into the core; and
optically coupling the second pump signal into the first cladding.

13. The method of claim 12 further comprising:
providing the fiber-based gain element such that the core comprises a first host material doped with a first active dopant; and
providing the fiber-based gain element such that the first cladding comprises a second host material that is doped with a second active dopant.

14. The method of claim 13 wherein the first and second active dopants are the same active dopant.

15. The method of claim 12 further comprising providing the fiber-based gain element such that it further includes a second cladding that is located between the core and the first cladding, wherein the core has a first refractive index, the first cladding has a second refractive index, and the second cladding has a third refractive index that is lower than the first refractive index and higher than the second refractive index.

16. The method of claim 15 further comprising providing the fiber-based gain element such that it further includes a third cladding that surrounds at least a portion of the first cladding, wherein the third cladding has a first refractive index that is lower than the second refractive index.

17. The method of claim 12 wherein the first arrangement arranges the first and second portions such that:
the first portion includes at least one first winding;
the second portion includes at least one second winding;
the at least one first winding includes a first region of the first outer surface;
the at least one second winding includes a second region of the second outer surface; and
the first region and second region are thermally coupled.

18. The method of claim 12 wherein the first arrangement arranges the first and second portions such that:
the first portion includes a plurality of first windings;
the second portion includes a plurality of second windings; and
the first and second windings are arranged in a close-packed arrangement in which each second winding of the plurality thereof is thermally coupled with at least one first winding of the plurality thereof.

19. The method of claim 12 further comprising providing a first material that is thermally conductive, wherein the first material is provided such that it is thermally coupled with each of the first outer surface and the second outer surface.

20. The method of claim 12 further comprising providing the first pump and the second pump, and wherein the fiber-based gain element, first pump, and

Assignees

• Univ Leland Stanford Junior

Inventors

• Digonnet Michel J
• Knall Jennifer

Classifications

• H01S3/094096 Primary

  Multi-wavelength pumping · CPC title

• H01S3/094007

  Cladding pumping, i.e. pump light propagating in a clad surrounding the active core · CPC title

• H01S3/0408

  Radiative cooling, e.g. by anti-Stokes scattering in the active medium · CPC title

• H01S3/06733

  Fibre having more than one cladding · CPC title

• H01S3/094053 Primary

  Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle · CPC title