DUAL-FREQUENCY OPTICAL SOURCE

• US 20150236789A1
• Filed: 01/26/2015
• Published: 08/20/2015
• Est. Priority Date: 01/24/2014
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: Kerry Vahala
• Inventors: Vahala, Kerry, Li, Jiang
• Granted Patent: US 9,537,571 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H03B 17/00 Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator
• CPC Class Codes: H03L 7/08 Details of the phase-locked loop
• CPC Class Codes: H03L 7/16 Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
• CPC Class Codes: H04B 10/2507 for the reduction or elimination of distortion or dispersion
• CPC Class Codes: H04B 10/2575 Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
• CPC Class Codes: H04B 10/25891 Transmission components H04B10/40 takes precedence
• CPC Class Codes: H04B 10/503 Laser transmitters
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means
• CPC Class Codes: H04L 7/0075 with photonic or optical means
• CPC Class Codes: H04L 7/0091 Transmitter details

Abstract

A dual-frequency optical source comprises: (a) first and second pump laser sources arranged to generate optical pump power at respective first and second pump laser frequencies v_pump1 and v_pump2; and (b) a fiber optical resonator characterized by a Brillouin shift frequency v_B and a free spectral range that is substantially equal to an integer submultiple of the Brillouin shift frequency. Each one of the first and second pump laser sources is frequency-locked to a corresponding resonant optical mode of the fiber optical resonator. First and second optical output signals of the dual-frequency optical reference source at respective first and second output frequencies v₁=v_pump1−v_B and v₂=v_pump2−v_B comprise stimulated Brillouin laser output generated by simultaneous optical pumping of the fiber optical resonator by the first and second pump laser sources, respectively. An output difference frequency v₂−v₁ is greater than about 300 GHz.

Claims

1. A dual-frequency optical source comprising:

(a) first and second pump laser sources arranged to generate optical pump power at respective first and second pump laser frequencies v_pump1 and v_pump2; and

(b) a fiber optical resonator characterized by a Brillouin shift frequency v_B and a free spectral range that is substantially equal to an integer submultiple of the Brillouin shift frequency,

wherein;

(c) each one of the first and second pump laser sources is frequency-locked to a corresponding resonant optical mode of the fiber optical resonator;

(d) first and second optical output signals of the dual-frequency optical reference source at respective first and second output frequencies v₁=v_pump1−

v_B and v₂=v_pump2−

v_B comprise stimulated Brillouin laser output generated by simultaneous optical pumping of the fiber optical resonator by the first and second pump laser sources, respectively; and

(e) an output difference frequency v₂−

v₁ is greater than about 300 GHz.

2. The dual-frequency optical source of claim 1 wherein the free spectral range of the fiber optical resonator is substantially equal to the Brillouin shift frequency of the fiber optical resonator.

3. The dual-frequency optical source of claim 1 wherein the fiber optical resonator comprises a fiber Fabry-Perot optical resonator.

4. The dual-frequency optical source of claim 1 wherein the fiber optical resonator comprises a fiber-loop optical resonator.

5. The dual-frequency optical source of claim 1 wherein the fiber optical resonator includes an optical fiber greater than or equal to about 40 meters long.

6. The dual-frequency optical source of claim 1 wherein the fiber optical resonator includes an optical fiber greater than or equal to about 100 meters long.

7. The dual-frequency optical source of claim 1 wherein the fiber optical resonator includes an optical fiber greater than or equal to about 200 meters long.

8. The dual-frequency optical source of claim 1 wherein the fiber optical resonator includes an optical fiber greater than or equal to about 500 meters long.

9. The dual-frequency optical source of claim 1 wherein the optical resonator comprises silica and the Brillouin shift frequency of the optical resonator is about 10.9 GHz.

10. The dual-frequency optical source of claim 1 wherein the output difference frequency v₂−

v₁ is greater than about 1 THz.

11. The dual-frequency optical source of claim 1 wherein the output difference frequency v₂−

v₁ is greater than about 10 THz.

12. The dual-frequency optical source of claim 1 wherein the output difference frequency v₂−

v₁ is greater than about 100 THz.

13. The dual-frequency optical source of claim 1 wherein the first and second optical reference frequencies v₁ and v₂ are each between about 75 THz and about 750 THz.

14. The dual-frequency optical source of claim 1 wherein the first and second optical reference frequencies v₁ and v₂ are each between about 120 THz and about 430 THz.

15. The dual-frequency optical source of claim 1 wherein the first and second optical reference frequencies v₁ and v₂ are each between about 150 THz and about 300 THz.

16. The dual-frequency optical source of claim 1 wherein the dual-frequency optical source is stabilized so as to (i) maintain fluctuations of the output difference frequency v₂−

v₁ within an operationally acceptable optical bandwidth or (ii) maintain phase noise of an optical signal at the output difference frequency within an operationally acceptable reference phase noise level.

17. The dual-frequency optical source of claim 16 wherein the operationally acceptable bandwidth is less than about 100 Hz over about a 1 second timescale.

18. The dual-frequency optical source of claim 16 wherein the operationally acceptable bandwidth is less than about 1 Hz over about a 1 second timescale.

19. The dual-frequency optical source of claim 16 wherein the operationally acceptable reference phase noise level is about −

40 dBc/Hz at 100 Hz offset frequency and about −

80 dBc/Hz at 10 kHz offset frequency.

20. The dual-frequency optical source of claim 16 wherein the operationally acceptable reference phase noise level is about −

80 dBc/Hz at 100 Hz offset frequency and about −

125 dBc/Hz at 10 kHz offset frequency.

21. The dual-frequency optical source of claim 16 wherein each one of the first and second pump laser sources is frequency-locked to the corresponding resonant optical mode of the resonator by a Pound-Drever-Hall mechanism.

22. A method for generating first and second optical output signals, the method comprising simultaneously pumping a fiber optical resonator with optical pump power from first and second pump laser sources, wherein:

(a) the first and second pump laser sources are arranged to generate optical pump power at respective first and second pump laser frequencies v_pump1 and v_pump2;

(b) the fiber optical resonator is characterized by a Brillouin shift frequency v_B and a free spectral range that is substantially equal to an integer submultiple of the Brillouin shift frequency;

(c) each one of the first and second pump laser sources is frequency-locked to a corresponding resonant optical mode of the fiber optical resonator;

(d) the first and second optical output signals are at respective first and second output frequencies v₁=v_pump1−

v_B and v₂=v_pump2−

v_B and comprise stimulated Brillouin laser output generated by the simultaneous optical pumping of the fiber optical resonator by the first and second pump laser sources, respectively; and

(e) an output difference frequency v₂−

v₁ is greater than about 300 GHz.