Systems and methods for optical frequency comb generation using a microring resonator

• US 9,891,500 B1
• Filed: 01/05/2017
• Issued: 02/13/2018
• Est. Priority Date: 01/05/2017
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Chu, Sai Tak, Zhu, Kun
• Primary Examiner(s): Petrovsek, Daniel
• Application Number:
  US15/399,321
• Time in Patent Office: 404 Days
• CPC Class Codes: G02F 1/3536 Four-wave interaction
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: G02F 2201/02 fibre
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/56 Frequency comb synthesizer
• CPC Class Codes: G02F 2203/70 Semiconductor optical amplifier [SOA] used in a device covered by G02F
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/06791 Fibre ring lasers fibre laser gyrometers G01C19/72
• CPC Class Codes: H01S 3/08013 Resonator comprising a fibre, e.g. for modifying dispersion or repetition rate the active medium being a fibre H01S3/067
• CPC Class Codes: H01S 5/0092 for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• CPC Class Codes: H01S 5/06821 Stabilising other output parameters than intensity or frequency, e.g. phase, polarisation or far-fields
• CPC Class Codes: H01S 5/5054 in which the wavelength is transformed by non-linear properties of the active medium, e.g. four wave mixing

Abstract

Systems and methods which provide for the generation of optical frequency combs using a microring resonator optical frequency comb generator configuration are described. A microring resonator optical frequency comb generator configuration of embodiments comprises a plurality of fiber loop laser cavities and at least one microring cavity are utilized. For example, an optical frequency comb generator may include a first fiber loop laser cavity, a second fiber loop laser cavity that is symmetrical with the first fiber loop laser cavity, and a microring resonator that is coupled into both of the first and second fiber loop laser cavities. The microring resonator may be configured to provide a high quality factor, Q, value. The microring resonator of embodiments works together with optical bandpass filters and amplifiers in the multiple fiber loops to make the generated optical frequency comb stable and flexible.

Claims

1. A system for optical frequency comb generation, the system comprising:

a first fiber loop laser cavity;

a second fiber loop laser cavity, wherein the second fiber loop laser cavity comprises a different fiber loop than the first fiber loop laser cavity; and

a microring resonator coupled to the first fiber loop laser cavity and the second fiber loop laser cavity, wherein the microring resonator is configured to use laser light from both the first and second fiber loop laser cavities with four wave mixing effect to generate an optical frequency comb.

2. The system of claim 1, wherein the first fiber loop laser cavity comprises:

a first optical amplifier;

a first polarization controller;

a first isolator,

a first optical bandpass filter; and

a first tap coupler.

3. The system of claim 2, wherein the first optical amplifier comprises a gain medium configured to sustain energy for laser oscillation.

4. The system of claim 2, wherein the first optical amplifier comprises a semiconductor optical amplifier.

5. The system of claim 2, wherein the first optical amplifier comprises an amplifier selected from the group consisting of:

an Erbium-doped fiber amplifier (EDFA);

an Ytterbium-doped fiber amplifier, and

a Raman amplifier.

6. The system of claim 2, wherein the first polarization controller is configured to control polarization of laser light provided to the microring resonator by the first fiber loop laser cavity.

7. The system of claim 6, wherein the first polarization controller is disposed in the first fiber loop laser cavity between the first optical amplifier and a terminal coupling the first fiber loop laser cavity to the microring resonator.

8. The system of claim 2, wherein the first isolator is configured to cause laser light to propagate in the first fiber loop laser cavity in a single direction.

9. The system of claim 2, wherein the first optical bandpass filter is configured to select a lasing mode of the first fiber loop laser cavity.

10. The system of claim 9, wherein the first optical bandpass filter is disposed in the first fiber loop laser cavity between the first optical amplifier and the first tap coupler.

11. The system of claim 9, wherein the first optical bandpass filter is a tunable optical bandpass filter.

12. The system of claim 2, wherein first tap coupler is configured to provide output of generated optical frequency comb signals.

13. The system of claim 12, wherein the first tap coupler comprises an optical coupler disposed in the first fiber loop laser cavity to output at least a portion of laser light of the first fiber loop laser cavity as output of the system.

14. The system of claim 2, wherein the second fiber loop laser cavity comprises:

a second optical amplifier;

a second polarization controller,

a second isolator, and

a second optical bandpass filter.

15. The system of claim 1, wherein the microring resonator comprises a microring resonator configuration providing a quality factor, Q, value of more than one million.

16. The system of claim 1, wherein the microring resonator comprises two terminals for laser light input and two terminals for laser light output, wherein the first fiber loop laser cavity is coupled to a first input terminal of the two terminals for laser light input and a first output terminal of the two terminals for laser light output, and wherein the second fiber loop laser cavity is coupled to a second input terminal of the two terminals for laser light input and a second output terminal of the two terminals for laser light output ports.

17. The system of claim 1, wherein the microring resonator is a tunable microring resonator.

18. The system of claim 17, wherein the tunable microring resonator comprises a thermal controller configured to tune a response of the tunable microring resonator.

19. A method for generating an optical frequency comb, the method comprising:

operating a first fiber loop laser cavity to provide sustained laser light of a first selected lasing mode;

operating a second fiber loop laser cavity to provide sustained laser light of a second selected lasing mode, wherein the second fiber loop laser cavity comprises a different fiber loop than the first fiber loop laser cavity; and

generating an optical frequency comb using a microring resonator coupled to the first fiber loop laser cavity and the second fiber loop laser cavity, wherein the generating the optical frequency comb uses laser light within the microring resonator having an intensity above a four wave mixing threshold to provide four wave mixing by the microring resonator.

20. The method of claim 19, wherein the operating the first fiber loop laser cavity and operating the second fiber loop laser cavity comprise:

controlling an output power of a first optical amplifier disposed in the first fiber loop laser cavity and an output power of a second optical amplifier disposed in the second fiber loop laser cavity to provide laser light within the first and second fiber loop laser cavities having the same level.

21. The method of claim 19, wherein the operating the first fiber loop laser cavity and operating the second fiber loop laser cavity comprise:

adjusting a first polarization controller disposed in the first fiber loop laser cavity and a second polarization controller disposed in the second fiber loop laser cavity to provide the same polarization of laser light to the microring resonator.

22. The method of claim 19, wherein the operating the first fiber loop laser cavity and operating the second fiber loop laser cavity comprise:

tuning a passband of a first optical bandpass filter disposed in the first fiber loop laser cavity and a passband of a second optical bandpass filter disposed in the second fiber loop laser cavity to different resonance peaks of the microring resonator to generate an optical frequency comb with a frequency spacing of an integer multiple of a free spectral range of the microring resonator.

23. The method of claim 19, wherein the operating the first fiber loop laser cavity, operating the second fiber loop laser cavity, and generating the optical frequency comb provides tunable frequency spacing and adjustable shape of the generated optical frequency comb.

24. The method of claim 23, wherein the operating the first fiber loop laser cavity and operating the second fiber loop laser cavity comprise:

changing a bandwidth of a first optical bandpass filter disposed in the first fiber loop laser cavity and a bandwidth of a second optical bandpass filter disposed in the second fiber loop laser cavity to select a number of lasing modes in the first and second fiber loop laser cavities.

25. The method of claim 24, wherein the changing a bandwidth of the first optical bandpass filter and the bandwidth of the second optical bandpass filter is changed to control an envelope shape of the generated optical frequency comb.

26. The method of claim 23, wherein the operating the first fiber loop laser cavity comprises:

tuning a passband of a first optical bandpass filter disposed in the first fiber loop laser cavity for changing a frequency spacing of the generated optical frequency comb.

27. The method of claim 19, further comprising:

tuning the microring resonator to change resonance frequencies of the microring resonator.

28. The method of claim 19, wherein the first fiber loop laser cavity includes a first optical amplifier configured to provide sustained energy for laser light oscillation in the first fiber loop laser cavity and a first optical bandpass filter configured to select the first lasing mode, wherein the second fiber loop laser cavity includes a second optical amplifier configured to provide sustained energy for laser light oscillation in the second fiber loop laser cavity and a second optical bandpass filter configured to select the second lasing mode, and wherein the microring resonator comprises a microring resonator configuration providing a quality factor, Q, value of more than one million.

29. An optical frequency comb generator comprising:

a first fiber loop laser cavity having a first optical amplifier, a first polarization controller, a first isolator, and a first optical bandpass filter; and

a second fiber loop laser cavity having a second optical amplifier, a second polarization controller, a second isolator, and a second optical bandpass filter, wherein the second fiber loop laser cavity comprises a different fiber loon than the first fiber boo laser cavity; and

a microring resonator coupled to the first and second fiber loop laser cavities and configured to store laser light from both the first and second fiber loop laser cavities and utilize four wave mixing effect with respect to the laser light to generate an optical frequency comb.

30. The optical frequency comb generator of claim 29, wherein the microring resonator comprises a microring resonator configuration providing a quality factor, Q, value of more than one million.

31. The optical frequency comb generator of claim 29, wherein the first optical bandpass filter is a tunable optical bandpass filter, wherein the microring resonator comprises a thermal controller configured to tune a response of the microring resonator.

32. The optical frequency comb generator 29, wherein the first fiber loop laser cavity further has a first tap coupler configured to output the generated optical frequency comb, and wherein the first fiber loop laser cavity and the second fiber loop laser cavity are symmetrical with respect to the microring resonator except for an absence of a tap coupler in the second fiber loop laser cavity.