Stabilized non-reciprocal fiber-ring brillouin laser source

Patent metadata

Field	Value
Publication number	US-10014649-B2
Application number	US-201615387089-A
Country	US
Kind code	B2
Filing date	Dec 21, 2016
Priority date	Dec 22, 2015
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A stabilized laser source includes a fiber-ring Brillouin laser that incorporates a circulator for non-reciprocal operation and for launching of a pump optical signal. Most of the pump optical signal is launched in a forward direction and drives Brillouin laser oscillation in the backward direction, a portion of which exits via an optical coupler as the optical output of the laser source. A small fraction of the pump optical signal is launched in the backward direction via the optical coupler, and a fraction of that backward-propagating pump optical signal exits via the optical coupler as an optical feedback signal. A frequency-locking mechanism receives the optical feedback signal and controls the pump optical frequency to maintain resonant propagation of the backward-propagating pump optical signal. A second pump optical signal can be launched in the forward direction to generate a second Brillouin laser oscillation.

First claim

What is claimed is:

1. A laser source comprising:
(a) a fiber-ring optical resonator including an optical circulator and an optical coupler, wherein the fiber-ring optical resonator is characterized by a Brillouin shift frequency ν B , and wherein the optical circulator is arranged so as to (i) limit to a single round trip propagation of an optical signal around the fiber-ring optical resonator in a forward direction, and (ii) permit resonant propagation of an optical signal around the fiber-ring optical resonator in a backward direction;
(b) a pump laser source that arranged so as to (i) produce a pump optical signal characterized by a pump optical frequency ν 1 , (ii) launch into the fiber-ring optical resonator via the optical circulator a first input portion of the pump optical signal to propagate in the forward direction, and (iii) launch into the fiber-ring optical resonator via the optical coupler a second input portion of the pump optical signal to propagate in the backward direction; and
(c) a frequency-locking mechanism coupling the pump laser source and the fiber-ring optical resonator, wherein the frequency-locking mechanism is arranged so as to control the pump optical frequency ν 1 to maintain resonant propagation of the second input portion of the pump optical signal around the fiber-ring optical resonator in the backward direction,
wherein:
(d) the fiber-ring optical resonator is arranged so as to produce from the first input portion of the pump optical signal a Brillouin laser optical signal, at a Brillouin laser frequency ν 1S =ν 1 −ν B , that resonantly propagates around the fiber-ring optical resonator in the backward direction; and
(e) the optical coupler is arranged so as to direct out of the fiber-ring optical resonator (i) an output portion of the second input portion of the pump optical signal, at the pump optical frequency ν 1 , to act as an optical feedback signal to the frequency-locking mechanism, and (ii) an output portion of the Brillouin laser optical signal, at the Brillouin laser frequency ν 1S , to act as optical output of the laser source.

2. The laser source of claim 1 wherein the pump optical frequency ν 1 is between about 75 THz and about 750 THz.

3. The laser source of claim 1 wherein the pump optical frequency ν 1 is between about 120 THz and about 430 THz.

4. The laser source of claim 1 wherein the pump optical frequency ν 1 is between about 150 THz and about 300 THz.

5. The laser source of claim 1 wherein the frequency-locking mechanism includes a Pound-Drever-Hall mechanism.

6. The laser source of claim 1 wherein the frequency-locking mechanism includes a Hänsch-Couillaud mechanism.

7. The laser source of claim 1 wherein the fiber-ring optical resonator includes an optical fiber greater than or equal to about 40 meters long.

8. The laser source of claim 1 wherein the fiber-ring optical resonator includes an optical fiber greater than or equal to about 100 meters long.

9. The laser source of claim 1 wherein the fiber-ring optical resonator includes an optical fiber greater than or equal to about 200 meters long.

10. The laser source of claim 1 wherein the fiber-ring optical resonator includes an optical fiber greater than or equal to about 500 meters long.

11. The laser source of claim 1 wherein the fiber-ring optical resonator comprises silica optical fiber and the Brillouin shift frequency ν B is about 10.9 GHz.

12. A method employing the laser source of claim 1 , the method comprising:
(A) launching from the pump laser source into the fiber-ring optical resonator via the optical circulator the first input portion of the pump optical signal, at the pump optical frequency ν 1 , to propagate in the forward direction and thereby produce, from the first input portion of the pump optical signal, the Brillouin laser optical signal, at the Brillouin laser frequency ν 1S =ν 1 −ν B , that resonantly propagates around the fiber-ring optical resonator in the backward direction;
(B) launching into the fiber-ring optical resonator via the optical coupler the second input portion of the pump optical signal to propagate in the backward direction;
(C) using the optical coupler, directing out of the fiber-ring optical resonator the output portion of the second input portion of the pump optical signal, at the pump optical frequency ν 1 , to act as the optical feedback signal to the frequency-locking mechanism;
(D) using the frequency-locking mechanism, controlling the pump optical frequency ν 1 to maintain resonant propagation of the second input portion of the pump optical signal around the fiber-ring optical resonator in the backward direction; and
(E) using the optical coupler, directing out of the fiber-ring optical resonator the output portion of the Brillouin laser optical signal, at the Brillouin laser frequency ν 1S , to act as the optical output of the laser source.

13. The laser source of claim 1 wherein:
(b′) the laser source further comprises a second pump laser source that is arranged so as to (i) produce a second pump optical signal characterized by a second pump optical frequency ν 2 , and (ii) launch into the fiber-ring optical resonator via the optical circulator a first input portion of the second pump optical signal to propagate in the forward direction;
(d′) the fiber-ring optical resonator is arranged so as to produce from the first input portion of the second pump optical signal a second Brillouin laser optical signal, at a second Brillouin laser frequency ν 2S =ν 2 −ν B , that resonantly propagates around the fiber-ring optical resonator in the backward direction; and
(e′) the optical coupler is arranged so as to direct out of the fiber-ring optical resonator an output portion of the second Brillouin laser optical signal, at the second Brillouin laser frequency ν 2S , to act as second optical output of the laser source.

14. The laser source of claim 13 wherein the pump frequency ν 1 and the second pump frequency ν 2 are each between about 75 THz and about 750 THz.

15. The laser source of claim 13 wherein the pump frequency ν 1 and the second pump frequency ν 2 are each between about 120 THz and about 430 THz.

16. The laser source of claim 13 wherein the pump frequency ν 1 and the second pump frequency ν 2 are each between about 150 THz and about 300 THz.

17. The laser source of claim 13 wherein the laser source is arranged so as to exhibit fluctuations of an output optical difference frequency |ν 2S −ν 1S | only within an operationally acceptable bandwidth.

18. The laser source of claim 13 wherein the laser source is arranged so as to exhibit fluctuations of an output optical difference frequency |ν 2S −ν 1S |, over about a 0.1 second timescale, only within a bandwidth less than about 100 Hz.

19. The laser source of claim 13 wherein the laser source is arranged so as to exhibit fluctuations of an output optical difference frequency |ν 2S −ν 1S |, over about a 0.1 second timescale, only within a bandwidth less than about 0.1 Hz.

20. The laser source of claim 13 wherein the second pump laser source includes at least one phase modulator operated at a frequency f M and arranged so as to generate, from at least a portion of the pump optical signal at the pump optical frequency ν 1 , the second pump optical signal at the second pump optical frequency ν 2 , and the second pump optical frequency is either ν 2 =ν 1 +f M or ν 2 =ν 1 −f M .

21. The laser source of claim 13 wherein pump laser source and the second pump las

Assignees

• California Inst Of Techn
• Hqphotonics Inc

Inventors

• Li Jiang
• Vahala Kerry

Classifications

• H01S3/06791 Primary

  Fibre ring lasers (fibre laser gyrometers G01C19/72) · CPC title

• H01S3/094049

  Guiding of the pump light · CPC title

• H01S3/1305

  Feedback control systems · CPC title

• H01S3/1109

  Active mode locking · CPC title

• H03B17/00

  Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator · CPC title