Tunable Lasers Locked to Whispering Gallery Mode Resonators

• US 20080310463A1
• Filed: 06/13/2008
• Published: 12/18/2008
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: Oewaves Incorporated
• Inventors: Ilchenko, Vladimir, Maleki, Lutfollah
• Granted Patent: US 7,991,025 B2
• Time in Patent Office: Days
• US Class Current: 372/20
• CPC Class Codes: H01S 3/082 defining a plurality of resonators, e.g. for mode selection or suppression
• CPC Class Codes: H01S 5/0656 Seeding, i.e. an additional light input is provided for controlling the laser modes, for example by back-reflecting light from an external optical component H01S5/14, H01S5/4062 and H01S5/4006 take precedence
• CPC Class Codes: H01S 5/1032 Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region

Abstract

Techniques and devices that stabilize a laser to a whispering gallery mode optical resonator.

Claims

1. A laser device, comprising:

a laser that is tunable in response to a control signal and produces a laser beam at a laser frequency; and

an optical resonator structured to support a whispering gallery mode circulating in the optical resonator, the optical resonator being optically coupled to the laser to receive a portion of the laser beam into the optical resonator in the whispering gallery mode and to feed laser light in the whispering gallery mode in the optical resonator back to the laser to stabilize the laser frequency at a frequency of the whispering gallery mode and to reduce a linewidth of the laser.

2. The laser device as in claim 1, wherein:

the optical resonator is tunable to stabilize the whispering gallery mode against environmental perturbations and the feedback of the laser light from the optical resonator to the laser transfers stability of the whispering gallery mode in the optical resonator to the laser.

3. The laser device as in claim 1, comprising:

a resonator tuning mechanism that controls and tunes the frequency of the whispering gallery mode to tune the laser frequency of the laser via the feedback of the laser light from the optical resonator to the laser.

4. The laser device as in claim 3, wherein:

the resonator tuning mechanism controls and tunes a temperature of the optical resonator to tune the laser frequency of the laser.

5. The laser device as in claim 3, wherein:

the resonator tuning mechanism applies and controls a pressure exerted on the optical resonator to tune the laser frequency of the laser.

6. The laser device as in claim 3, wherein:

the optical resonator comprises an electro-optic material that changes a refractive index in response to an electrical potential applied to the optical resonator; and

the resonator tuning mechanism applies and controls the electrical potential to tune the laser frequency of the laser.

7. The laser device as in claim 6, wherein:

the resonator tuning mechanism is configured to modulate the electrical potential to modulate the frequency of the whispering gallery mode of the optical resonator and the laser frequency of the laser.

8. The laser device as in claim 6, comprising:

a control mechanism to both adjust the frequency of the whispering gallery mode of the optical resonator via the resonator tuning mechanism and to adjust the laser frequency of the laser while stabilizing the laser frequency at the frequency of the whispering gallery mode.

9. The laser device as in claim 1, comprising:

an optical coupler evanescently coupled to the optical resonator to couple light into and light out of the whispering gallery mode in the optical resonator; and

a lens assembly optically coupled between the laser and the optical coupler to direct the laser beam to the optical coupler and to direct the laser light from the optical resonator into the laser.

10. The laser device as in claim 9, wherein:

the lens assembly comprises a first GRIN lens located next to the laser and configured to have a small aperture to focus light into the laser and to collect light from the laser, and a second GRIN lens located next to the optical coupler and configured to have a large aperture to focus light into the optical coupler and to collect light from the optical coupler.

11. The laser device as in claim 10, wherein:

the optical coupler comprises a prism.

12. A method for controlling a laser with a whispering gallery mode optical resonator, comprising:

coupling a laser output from a laser, that is tunable in response to a control signal to tune a laser frequency of the laser output, into an optical resonator, which is made of an electrical-optic material to support a whispering gallery mode, and laser light out of laser light in the whispering gallery mode;

injecting the laser light coupled out of the optical resonator back into the laser to stabilize the laser frequency at a frequency of the whispering gallery mode and to reduce a linewidth of the laser; and

controlling at least one of the control signal to the laser and an electrical voltage applied to the electrical-optic material of the optical resonator to tune the laser frequency while stabilizing the laser frequency at the frequency of the whispering gallery mode.

13. The method as in claim 12, comprising:

modulating the electrical voltage applied to the electrical-optic material of the optical resonator to modulate the laser frequency.

14. The method as in claim 12, comprising:

modulating the electrical voltage applied to the electrical-optic material of the optical resonator to modulate the laser output out of the laser; and

during the modulating, simultaneously tuning the control signal to the laser to tune the laser frequency.

15. A laser device, comprising:

a base plate;

a semiconductor laser mounted on the base plate, that is tunable in response to a electrical laser control signal and produces a laser beam at a laser frequency;

an optical resonator mounted on the base plate, the optical resonator made of an electrical-optic material to support light in a whispering gallery mode circulating along first and second directions opposite to each other in the optical resonator;

an optical coupler mounted on the base plate, optically coupled to the optical resonator to evanescently couple laser light of the laser beam from the laser into the optical resonator as laser light in the whispering gallery mode and evanescently couple laser light out of the optical resonator to produce feedback laser light;

a lens assembly mounted on the base plate, optically coupled between the laser and the optical coupler to direct the laser beam from the laser to the optical coupler and to direct the feedback laser light from the optical coupler into the laser;

an electrode formed on the optical resonator to receive an electrical resonator control signal; and

an electrical feed conductor on the base plate to supply the electrical resonator control signal to the electrode on the optical resonator.

16. The laser device as in claim 15, comprising:

an optical transparent plate mounted on the base plate in an optical path between the laser and the optical resonator and adjustable to change a height of the laser beam from the base plate.

17. The laser device as in claim 15, comprising:

an RF circuit to produce an RF modulation signal to the electrical feed conductor to modulate the optical resonator to cause an RF modulation in the laser beam.

18. The laser device as in claim 15, comprising:

a position control module engaged to the optical coupler and operable to control a gap between the optical coupler and the optical resonator.

19. The laser device as in claim 15, wherein the optical coupler couples a laser output beam from the optical resonator, and the laser device comprises an optical isolator mounted on the base plate to receive a laser output beam to as an output laser beam of the laser device.