Laser Cavity Exhibiting Low Noise

• US 20130161295A1
• Filed: 09/02/2011
• Published: 06/27/2013
• Est. Priority Date: 09/02/2010
• Status: Abandoned Application

• Current Assignee: OFS Fitel LLC (Furukawa Electric Company Limited)
• Original Assignee: OFS Fitel LLC (Furukawa Electric Company Limited)
• Inventors: Tominaga, Keisuke
• Application Number:
  US13/819,110
• Publication Number:
  US 20130161295A1
• Time in Patent Office: Days
• US Class Current: 219/85.13
• CPC Class Codes: H01S 2301/03 Suppression of nonlinear conversion, e.g. specific design to suppress for example stimulated brillouin scattering [SBS], mainly in optical fibres in combination with multimode pumping
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/08045 Single-mode emission
• CPC Class Codes: H01S 3/094011 with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
• CPC Class Codes: H01S 3/09408 Pump redundancy
• CPC Class Codes: H01S 3/1618 ytterbium

Abstract

Inventive single cavities for use in a high power fiber laser systems are described that include a high reflective grating, a gain fiber, an output coupler having a bandwidth in the range of 1 nm to 2 nm; and an output fiber connected to the single cavity that supplies power from the single cavity. The single cavity can be used in a wide variety of applications, including welding, cutting, brazing or drilling a material, or to seed a downstream amplifier.

Claims

1. A cavity for use in a high power fiber laser system, comprising:

a reflective grating;

a gain fiber;

an output coupler, the output coupler having a bandwidth in the range of 1 nm to 2 nm; and

an output fiber connected to the single cavity laser that supplies power from the single cavity.

2. The cavity of claim 1, further comprising a pump diode.

3. The cavity of claim 1, wherein the bandwidth of the output coupler is in the range of 1.2 nm to 2 nm.

4. The cavity of claim 1, wherein the bandwidth of the output coupler is in the range of 1.4 to 2 nm.

5. The cavity of claim 1, wherein the bandwidth of the output coupler is in the range of 1.6 to 2 nm.

6. The cavity of claim 1, wherein the high reflective grating and the output coupler comprise Bragg gratings.

7. The cavity of claim 1, wherein the output fiber is a multimode fiber.

8. The cavity of claim 1, further comprising a pump source to introduce pump light into the gain fiber, the pump source comprising a plurality of pump diodes connected to the single cavity through a pump combiner.

9. The cavity of claim 8, wherein the wavelengths of the pump diodes are in the range of 900 nm to 990 nm.

10. The cavity of claim 8, wherein the number of longitudinal modes in the laser cavity is increased compared to a system that uses an output coupler having a lower bandwidth.

11. The cavity of claim 10, wherein nonlinear effects caused by Stimulated Raman scattering are reduced compared to a single cavity laser that uses an output coupler having a lower bandwidth.

12. The cavity of claim 1, wherein the slope efficiency of the cavity is in the range of 65% to 70%.

13. The cavity of claim 1, wherein the gain fiber comprises a rare earth doped fiber.

14. The cavity of claim 1, wherein the gain fiber has a length of 25 meters or greater.

15. The cavity of claim 1, wherein the gain fiber has a mode field diameter of less than 12 microns.

16. The cavity of claim 8, wherein the pump source provides a power such that the output power of the cavity exceeds 250 Watts.

17. The cavity of claim 1, wherein the pump source has a mean pump wavelength in the range of 900 to 1000 nm.

18. A fiber laser system comprising the single cavity laser of claim 1 and a downstream amplifier seeded by the single cavity.

19. A device for welding, cutting, brazing or drilling a material comprising the single cavity laser of claim 1.

20. A method of reducing Stimulated Raman Scattering (SRS) in of a high power single cavity fiber laser having an output power exceeding 250 Watts comprising optically coupling a fiber amplifier to an output coupler having a bandwidth in the range of 1 nm to 2 nm such that the number of longitudinal modes in the laser cavity are increased to reduce the SRS of laser compared to a single cavity fiber laser having a lower bandwidth.

21. A method of treating an object, comprising:

operating a single cavity laser having a high reflective grating, a gain fiber, an output coupler having a bandwidth in the range of 1 nm to 2 nm and an output fiber connected to the single cavity laser to supply at least 250 Watts of power from the single cavity laser; and

applying the at least 250 Watts of power from the single cavity laser to the object.

22. The method of claim 21, wherein the object is cut, welded, brazed, and/or drilled by the single cavity laser.