Dual-frequency optical source

• US 9,537,571 B2
• Filed: 01/26/2015
• Issued: 01/03/2017
• Est. Priority Date: 01/24/2014
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Li, Jiang, Vahala, Kerry
• Primary Examiner(s): Payne, David
• Assistant Examiner(s): Motsinger, Tanya
• Application Number:
  US14/605,987
• Publication Number:
  US 20150236789A1
• Time in Patent Office: 708 Days
• Field of Search: 372/94, 398/200, 398/201
• 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:

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

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

wherein 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,

wherein an output difference frequency v₂−

v₁ is greater than about 300 GHz, and

wherein the fiber optical resonator includes an optical fiber greater than or equal to about 100 meters long.

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 200 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 500 meters long.

7. 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.

8. 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.

9. 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.

10. 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.

11. A method for generating first and second optical output signals using the dual-frequency optical source of claim 1, the method comprising simultaneously pumping the 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.

12. A dual-frequency optical source, comprising:

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

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

wherein 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,

wherein the output difference frequency v₂−

v₁ is greater than about 1 THz.

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

v₁ is greater than about 10 THz.

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

v₁ is greater than about 100 THz.

15. A dual-frequency optical source, comprising:

first and second pump laser sources arranged to generate optical pump power at respective first and second pump laser frequencies v_pump1and v_pump2; and

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

wherein 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,

wherein an output difference frequency v₂−

v₁ is greater than about 300 GHz,

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; and

wherein the operationally acceptable bandwidth is less than about 100 Hz over about a 1 second timescale.

16. The dual-frequency optical source of claim 15 wherein the operationally acceptable bandwidth is less than about 1 Hz over about a 1 second timescale.

17. The dual-frequency optical source of claim 15 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.

18. The dual-frequency optical source of claim 15 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.

19. The dual-frequency optical source of claim 15 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.