External cavity laser with reduced optical mode-hopping

Patent metadata

Field	Value
Publication number	US-9837781-B2
Application number	US-201514714078-A
Country	US
Kind code	B2
Filing date	May 15, 2015
Priority date	Oct 24, 2014
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

An optical source is described. This optical source includes a semiconductor optical amplifier (with a semiconductor other than silicon) that provides an optical gain medium and that includes a reflector. Moreover the hybrid external cavity laser includes a photonic chip with: an optical waveguide that conveys an optical signal output by the semiconductor optical amplifier; and a ring resonator, having a resonance wavelength, which reflects at least a resonance wavelength in the optical signal, where the reflector and the ring resonator define an optical cavity. Furthermore, the photonic chip includes: a thermal-tuning mechanism that adjusts the resonance wavelength; a photo-detector that measures an optical power output by the ring resonator; and control logic that adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength.

First claim

What is claimed is:

1. An optical source, comprising:
a semiconductor optical amplifier defined in a semiconductor other than silicon and having a first edge and a second edge, wherein the semiconductor optical amplifier includes a reflective coating on the first edge, and wherein the semiconductor optical amplifier is configured to provide an optical signal at the second edge; and
a photonic chip optically coupled to the semiconductor optical amplifier, wherein the photonic chip includes:
an optical waveguide configured to convey the optical signal;
a ring resonator, optically coupled to the optical waveguide and having a resonance wavelength, configured to reflect at least the resonance wavelength in the optical signal, wherein the reflective coating and the ring resonator define an optical cavity;
a thermal-tuning mechanism, thermally coupled to the ring resonator, configured to adjust the resonance wavelength;
a photo-detector, optically coupled to an output of the ring resonator, configured to measure optical power output by the ring resonator; and
control logic, electrically coupled to the thermal-tuning mechanism and the photo-detector, configured to adjust the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength
wherein the optical source further includes a temperature-compensation element, optically coupled to the optical waveguide, configured to compensate for a temperature dependence of indexes of refraction of the optical waveguide.

2. The optical source of claim 1 , wherein the semiconductor optical amplifier is edge-coupled to the photonic chip.

3. The optical source of claim 1 , wherein the semiconductor optical amplifier is surface-normal coupled to the photonic chip.

4. The optical source of claim 1 , wherein the photonic chip includes:
a substrate;
a buried-oxide layer disposed on the substrate; and
a semiconductor layer disposed on the buried-oxide layer, wherein the optical waveguide and the ring resonator are defined in the semiconductor layer.

5. The optical source of claim 4 , wherein the substrate, the buried-oxide layer and the semiconductor layer constitute a silicon-on-insulator technology.

6. The optical source of claim 1 , wherein the optical source further includes a directional coupler optically coupled to the optical waveguide; and
wherein an output optical signal is output from the optical source at an edge of the direction coupler.

7. The optical source of claim 1 , wherein the control logic is configured to adjust the temperature of the ring resonator to minimize the measured optical power.

8. The optical source of claim 1 , wherein the optical source further includes at least a temperature sensor, electrically coupled to the control logic, configured to determine a parameter associated with a temperature; and
wherein the control logic is configured to modify a phase in the optical cavity to adjust the carrier wavelength based on the determined parameter.

9. The optical source of claim 8 , wherein the parameter is associated with at least one of: a temperature of the semiconductor optical amplifier; and a temperature of the photonic chip.

10. The optical source of claim 8 , wherein the phase is modified in one of: the semiconductor optical amplifier; and the photonic chip.

11. The optical source of claim 8 , wherein the control logic modifies the phase based on a predefined table of temperatures and associated carrier wavelengths.

12. The optical source of claim 1 , wherein the optical source further includes at least an interferometer, electrically coupled to the control logic, configured to determine the carrier wavelength; and
wherein the control logic is configured to modify a phase in the optical cavity to adjust the carrier wavelength based on the determined carrier wavelength.

13. The optical source of claim 1 , wherein the temperature-compensation element includes a titanium-dioxide optical waveguide.

14. A system, comprising:
a processor;
memory, coupled to the processor, configured to store a program module; and
an optical source, wherein the optical source includes:
a semiconductor optical amplifier defined in a semiconductor other than silicon and having a first edge and a second edge, wherein the semiconductor optical amplifier includes a reflective coating on the first edge, and wherein the semiconductor optical amplifier is configured to provide an optical signal at the second edge; and
a photonic chip optically coupled to the semiconductor optical amplifier, wherein the photonic chip includes:
an optical waveguide configured to convey the optical signal;
a ring resonator, optically coupled to the optical waveguide and having a resonance wavelength, configured to reflect at least the resonance wavelength in the optical signal, wherein the reflective coating and the ring resonator define an optical cavity;
a thermal-tuning mechanism, thermally coupled to the ring resonator, configured to adjust the resonance wavelength;
a photo-detector, optically coupled to an output of the ring resonator, configured to measure optical power output by the ring resonator; and
control logic, electrically coupled to the thermal-tuning mechanism and the photo-detector, configured to adjust the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength
wherein the optical source further includes a temperature-compensation element, optically coupled to the optical waveguide, configured to compensate for a temperature dependence of indexes of refraction of the optical waveguide.

15. The system of claim 14 , wherein the optical source further includes a directional coupler optically coupled to the optical waveguide; and
wherein an output optical signal is output from the optical source at an edge of the direction coupler.

16. The system of claim 14 , wherein the control logic is configured to adjust the temperature of the ring resonator to minimize the measured optical power.

17. The system of claim 14 , wherein the optical source further includes at least a temperature sensor, electrically coupled to the control logic, configured to determine a parameter associated with a temperature of at least one of: the semiconductor optical amplifier; and the photonic source; and
wherein the control logic is configured to modify a phase in the optical cavity to adjust the carrier wavelength based on the determined parameter.

18. The system of claim 14 , wherein the optical source further includes at least an interferometer, electrically coupled to the control logic, configured to determine the carrier wavelength; and
wherein the control logic is configured to modify a phase in the optical cavity to adjust the carrier wavelength based on the determined carrier wavelength.

19. A method for locking a cavity mode for an external cavity laser, the method comprising:
generating an optical signal in a semiconductor optical amplifier defined in a semiconductor other than silicon, wherein the semiconductor optical amplifier includes a reflective coating on a first edge, and wherein the semiconductor optical amplifier provides the optical signal at a second edge;
conveying the optical signal in an optical waveguide on a photonic chip;
reflecting at least a resonance wavelength in the optical signal using a ring resonator having the resonance wavelength, wherein the reflective coating and the ring resonator define an optical cavity;

Assignees

• Oracle Int Corp

Inventors

• Krishnamoorthy Ashok V
• Lee Jin-Hyoung
• Zheng Xuezhe

Classifications

• H01S3/083

  Ring lasers {(fibre ring lasers H01S3/06791)} · CPC title

• H01S5/06255

  Controlling the frequency of the radiation · CPC title

• H01S5/0612

  controlled by temperature · CPC title

• H01S5/0654

  Single longitudinal mode emission · CPC title

• H01S5/142 Primary

  which comprises an additional resonator · CPC title