Wavelength control of a dual-ring laser

• US 9,608,406 B1
• Filed: 01/22/2016
• Issued: 03/28/2017
• Est. Priority Date: 01/22/2016
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Lee, Jin-Hyoung, Zheng, Xuezhe, Krishnamoorthy, Ashok V.
• Primary Examiner(s): Nguyen, Tuan
• Application Number:
  US15/004,569
• Time in Patent Office: 431 Days
• Field of Search: 359/344
• US Class Current: 1/1
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/29341 Loop resonators operating in a whispering gallery mode evanescently coupled to a light guide, e.g. sphere or disk or cylinder evanescent coupling for sensing fluorescence G01N21/648
• CPC Class Codes: H01S 5/026 Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers stabilisation of output H01S5/06
• CPC Class Codes: H01S 5/0261 Non-optical elements, e.g. laser driver components, heaters H01S5/0265 takes precedence
• CPC Class Codes: H01S 5/0612 controlled by temperature
• CPC Class Codes: H01S 5/06255 Controlling the frequency of the radiation
• CPC Class Codes: H01S 5/1007 Branched waveguides
• 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
• CPC Class Codes: H01S 5/142 which comprises an additional resonator

Abstract

An optical source includes a semiconductor optical amplifier that provides an optical signal, and a photonic chip with first and second ring resonators that operate as Vernier rings. When the optical source is operated below a lasing threshold, one or more thermal-tuning mechanisms, which may be thermally coupled to the first ring resonator and/or the second ring resonator, may be adjusted to align resonances of the first ring resonator and the second ring resonator based on measured optical power on a shared optical waveguide that is optically coupled to the first and second ring resonators. Then, when the optical source is operated above the lasing threshold, a common thermal-tuning mechanism may be adjusted to lock the aligned resonances with an optical cavity mode of the optical source based on a measured optical power on an optical waveguide that is optically coupled to the first ring resonator.

Claims

1. An optical source, comprising:

a semiconductor optical amplifier defined in a semiconductor other than silicon, wherein the semiconductor optical amplifier has a first edge and a second edge, includes a reflective coating on the first edge, and, during operation, provides an optical signal at the second edge; and

a photonic chip optically coupled to the semiconductor optical amplifier, wherein the photonic chip includes;

a first optical waveguide having a third edge, optically coupled to the second edge of the semiconductor optical amplifier, and a fourth edge;

a first ring resonator optically coupled to the first optical waveguide;

a second optical waveguide, optically coupled to the first ring resonator, having a fifth edge and a sixth edge optically coupled to a first termination;

a second ring resonator optically coupled to the second optical waveguide;

a common thermal-tuning mechanism thermally coupled to the first ring resonator and the second ring resonator;

a first thermal-tuning mechanism thermally coupled to the first ring resonator;

a second thermal-tuning mechanism thermally coupled to the second ring resonator;

a monitoring device optically coupled to the fourth edge and the fifth edge; and

control logic, electrically coupled to the monitoring device, the common thermal-tuning mechanism, the first thermal-tuning mechanism and the second thermal-tuning mechanism, that, during operation, tunes the first ring resonator and the second ring resonator.

2. The optical source of claim 1, wherein the control logic tunes the first ring resonator and the second ring resonator by:

adjusting, when the optical source is operated below a lasing threshold, at least one of the first thermal-tuning mechanism and the second thermal-tuning mechanism to align a first resonance of the first ring resonator and a second resonance of the second ring resonator based on a measured optical power at the fifth edge; and

adjusting, when the optical source is operated above the lasing threshold, the common thermal-tuning mechanism to lock the aligned first and second resonances with an optical cavity mode of the optical source having a carrier wavelength based on a measured optical power at the fourth edge.

3. The optical source of claim 2, wherein, during operation, the control logic maintains the alignment of the first and second resonances with the optical cavity mode by:

adjusting the common thermal-tuning mechanism to minimize the measured output power at the fourth edge; and

adjusting at least one of the first thermal-tuning mechanism and the second thermal-tuning mechanism to minimize the measured output power at the fifth edge.

4. The optical source of claim 2, wherein the first and the second resonances are aligned by minimizing the measured optical power at the fifth edge.

5. The optical source of claim 2, wherein the first and the second resonances are aligned by minimizing the measured optical power at the fourth edge.

6. The optical source of claim 1, wherein the semiconductor optical amplifier is one of:

edge coupled to the photonic chip; and

surface-normal coupled to the photonic chip.

7. The optical source of claim 1, wherein a given thermal-tuning mechanism includes one of:

a doped semiconductor heater; and

a metal heater.

8. The optical source of claim 1, wherein the optical source further comprises a phase modulator optically coupled to the first optical waveguide.

9. 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 optical components are defined in the semiconductor layer.

10. The optical source of claim 9, wherein the substrate, the buried-oxide layer and the semiconductor layer constitute a silicon-on-insulator technology.

11. A system, comprising:

a processor;

a memory coupled to the processor; and

an optical source, wherein the optical source includes;

a semiconductor optical amplifier defined in a semiconductor other than silicon, wherein the semiconductor optical amplifier has a first edge and a second edge, includes a reflective coating on the first edge, and, during operation, provides an optical signal at the second edge; and

a photonic chip optically coupled to the semiconductor optical amplifier, wherein the photonic chip includes;

a first optical waveguide having a third edge, optically coupled to the second edge of the semiconductor optical amplifier, and a fourth edge;

a first ring resonator optically coupled to the first optical waveguide;

a second optical waveguide, optically coupled to the first ring resonator, having a fifth edge and a sixth edge optically coupled to a first termination;

a second ring resonator optically coupled to the second optical waveguide;

a common thermal-tuning mechanism thermally coupled to the first ring resonator and the second ring resonator;

a first thermal-tuning mechanism thermally coupled to the first ring resonator;

a second thermal-tuning mechanism thermally coupled to the second ring resonator;

a monitoring device optically coupled to the fourth edge and the fifth edge; and

control logic, electrically coupled to the monitoring device, the common thermal-tuning mechanism, the first thermal-tuning mechanism and the second thermal-tuning mechanism, that, during operation, tunes the first ring resonator and the second ring resonator.

12. The system of claim 11, wherein the control logic tunes the first ring resonator and the second ring resonator by:

adjusting, when the optical source is operated below a lasing threshold, at least one of the first thermal-tuning mechanism and the second thermal-tuning mechanism to align a first resonance of the first ring resonator and a second resonance of the second ring resonator based on a measured optical power at the fifth edge; and

adjusting, when the optical source is operated above the lasing threshold, the common thermal-tuning mechanism to lock the aligned first and second resonances with an optical cavity mode of the optical source having a carrier wavelength based on a measured optical power at the fourth edge.

13. The system of claim 12, wherein, during operation, the control logic maintains the alignment of the first and second resonances with the optical cavity mode by:

adjusting the common thermal-tuning mechanism to minimize the measured output power at the fourth edge; and

adjusting at least one of the first thermal-tuning mechanism and the second thermal-tuning mechanism to minimize the measured output power at the fifth edge.

14. The system of claim 13, wherein the first and second ring-resonances are aligned by minimizing the measured optical power at the fifth edge.

15. The system of claim 13, wherein the first and second ring-resonances are aligned by minimizing the measured optical power at the fourth edge.

16. The system of claim 11, wherein the optical source further comprises a phase modulator optically coupled to the first optical waveguide.

17. The system of claim 11, wherein a given thermal-tuning mechanism includes one of:

a doped semiconductor heater; and

a metal heater.

18. The system of claim 11, 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 optical components are defined in the semiconductor layer.

19. The system of claim 18, wherein the substrate, the buried-oxide layer and the semiconductor layer constitute a silicon-on-insulator technology.

20. A method for tuning an optical source that includes a first ring resonator and a second ring resonator that operate as Vernier rings, the method comprising:

conveying an optical signal from a semiconductor optical amplifier in a first optical waveguide;

optically coupling the optical signal from the first optical waveguide to a second optical waveguide via the first ring resonator;

conveying the optical signal in the second optical waveguide;

optically coupling the optical signal from the second optical waveguide to a third optical waveguide via a second ring resonator;

adjusting, when the optical source is operated below a lasing threshold, one of a first thermal-tuning mechanism, which is thermally coupled to the first ring resonator, and a second thermal-tuning mechanism, which is thermally coupled to the second ring resonator, to align a first resonance of the first ring resonator and a second resonance of the second ring resonator based on a measured optical power at an edge of the second optical waveguide; and

adjusting, when the optical source is operated above the lasing threshold, a common thermal-tuning mechanism to lock the aligned first and second resonances with an optical cavity mode of the optical source having a carrier wavelength based on a measured optical power at an edge of the first optical waveguide.