Methods for SRS protection of laser components and apparatus providing SRS protection

Patent metadata

Field	Value
Publication number	US-12142889-B2
Application number	US-201917419510-A
Country	US
Kind code	B2
Filing date	Dec 31, 2019
Priority date	Dec 31, 2018
Publication date	Nov 12, 2024
Grant date	Nov 12, 2024

Abstract

Apparatus include a first optical fiber including a core situated to propagate a signal beam at a signal wavelength and an unwanted stimulated Raman scattering (SRS) beam at an SRS wavelength associated with the signal wavelength, and a fiber Bragg grating (FBG) situated in a core of a second optical fiber optically coupled to the core of the first optical fiber, the FBG having a selected grating reflectivity associated with the SRS wavelength and being situated to reflect the SRS beam back along the core of the second optical fiber and to reduce a damage associated with propagation of the SRS beam to power sensitive laser system components optically coupled to the second optical fiber. Methods are also disclosed.

First claim

We claim:

1. An apparatus, comprising:
a first optical fiber including a core situated to propagate a signal beam at a signal wavelength and an unwanted stimulated Raman scattering (SRS) beam at an SRS wavelength associated with the signal wavelength; and
a fiber Bragg grating (FBG) situated in a core of a second optical fiber optically coupled to the core of the first optical fiber, the FBG having a selected grating reflectivity associated with the SRS wavelength and being situated to reflect the SRS beam back along the core of the second optical fiber and to reduce a damage associated with propagation of the SRS beam to power sensitive laser system components optically coupled to the second optical fiber,
wherein the second optical fiber comprises a length of optical fiber that is situated between (i) a high reflector of a laser oscillator situated to generate and direct an output beam away from the second optical fiber and (ii) an optical power sensitive component that is optically coupled to a core of the laser oscillator so as to copropagate with the output beam.

2. The apparatus of claim 1 , wherein the SRS beam is associated with at least one SRS event.

3. The apparatus of claim 1 , further comprising a fused pump combiner situated to receive one or more pump beams propagating in respective pump fibers optically coupled to corresponding positions of an input end of the fused pump combiner, wherein the pump combiner is optically coupled to the first optical fiber so as to direct the one or more pump beams into the first optical fiber.

4. The apparatus of claim 3 , further comprising one or more pump modules with respective pump fibers optically coupled to the fused pump combiner.

5. The apparatus of claim 1 , further comprising a gain fiber situated to generate the signal beam and optically coupled to the first optical fiber, wherein the FBG is situated adjacent to an input end or an output end of the gain fiber.

6. The apparatus of claim 1 , wherein the FBG has a grating orientation perpendicular to an optical axis of the core of the first optical fiber.

7. The apparatus of claim 1 , wherein the second optical fiber corresponds to at least a portion of a gain fiber situated to generate the signal beam.

8. The apparatus of claim 1 , wherein the second optical fiber comprises a length of passive fiber that includes an oscillator FBG situated in the core of the passive fiber that is highly reflective at the signal wavelength associated with an oscillator optically coupled to or part of the second fiber.

9. The apparatus of claim 1 , wherein the second optical fiber comprises a length of passive fiber that includes an oscillator FBG situated in the core that is partially reflective at a laser wavelength associated with an oscillator optically coupled to or part of the second fiber.

10. The apparatus of claim 1 , further comprising a gain fiber optically coupled to the second optical fiber and wherein the second optical fiber comprises a length of optical fiber optically coupled to an output of the gain fiber and an end of the first optical fiber.

11. The apparatus of claim 1 , further comprising a fused fiber combiner optically coupled between the high reflector and the optical power sensitive component.

12. The apparatus of claim 11 , wherein the FBG is situated between the fused fiber combiner and the laser oscillator and/or between the fused fiber combiner and the optical power sensitive component.

13. The apparatus of claim 1 , wherein the first optical fiber and the second optical fiber comprise a continuous length of optical fiber.

14. The apparatus of claim 1 , wherein the SRS beam has a wavelength corresponding to the SRS wavelength of an associated output beam having an average output power of 1 kW or greater.

15. A method, comprising:
producing with a fiber laser oscillator a laser beam that propagates in a first direction through an optical fiber having a core, the optical fiber comprising a first optical fiber coupled to a second optical fiber to produce an output beam; and
reflecting an stimulated Raman scattering (SRS) beam propagating in a second direction opposite the first direction along the core of the optical fiber of the fiber laser oscillator so that the SRS beam propagates back along the core of the optical fiber and away from power sensitive laser system components, with an SRS fiber Bragg grating (FBG) situated to reduce damage associated with receiving of the SRS beam by the power sensitive laser system components,
wherein the second optical fiber comprises a length of optical fiber that is situated between (i) a high reflector of the fiber laser oscillator situated to generate and direct the output beam away from the second optical fiber and (ii) an optical power sensitive component that is optically coupled to a core of the laser oscillator so as to copropagate with the output beam.

16. The method of claim 15 , wherein the power sensitive laser system (Original) components include at least one of a fused fiber combiner or a pump module.

17. A method, comprising:
situating in a fiber laser system configured to produce a signal beam at a signal wavelength a fiber Bragg grating (FBG) configured to be reflective at a stimulated Raman scattering (SRS) wavelength of the signal wavelength so that an SRS beam that propagates in a fiber core of the fiber laser system is reflected so as to propagate back along the fiber core and away from power sensitive laser system components of the fiber laser system so as to reduce a damage associated with receiving of the SRS beam by the power sensitive laser system components,
wherein the fiber laser system comprises an optical fiber having a core, the optical fiber comprising a first optical fiber coupled to a second optical fiber to produce an output beam, and
wherein the second optical fiber comprises a length of optical fiber that is situated between (i) a high reflector of the fiber laser oscillator situated to generate and direct the output beam away from the second optical fiber and (ii) an optical power sensitive component that is optically coupled to a core of the laser oscillator so as to copropagate with the output beam.

18. The method of claim 17 , wherein the power sensitive laser system components include one or more of a fused fiber combiner or one or more pump modules.

Assignees

• Nlight Inc

Inventors

• Fanning C Geoffrey
• Small Jay
• Kliner Dahv A V
• Rivera Chris A

Classifications

• H01S3/094053

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

• H01S3/094007

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

• H01S3/08013

  Resonator comprising a fibre, e.g. for modifying dispersion or repetition rate (the active medium being a fibre H01S3/067) · CPC title

• H01S3/0675

  Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers · CPC title

• G02B6/29317

  Light guides of the optical fibre type · CPC title