Mode-hop-free hybrid external-cavity laser with passive thermo-optic coefficient compensation

Patent metadata

Field	Value
Publication number	US-9871346-B1
Application number	US-201715425889-A
Country	US
Kind code	B1
Filing date	Feb 6, 2017
Priority date	Sep 22, 2016
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

The disclosed embodiments relate to a system that implements a hybrid laser. This system includes a reflective gain medium (RGM) comprising an optical gain material coupled to a mirror. This RGM is coupled to a spot-size converter (SSC), which optically couples the RGM to an optical reflector through a silicon waveguide. The SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide. During operation, the RGM, the spot-size converter, the silicon waveguide and the silicon mirror collectively form a lasing cavity, wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon. Finally, a laser output is optically coupled out of the lasing cavity.

First claim

What is claimed is:

1. A hybrid laser, comprising:
a reflective gain medium (RGM) comprising an optical gain material coupled with an associated reflector;
a silicon waveguide;
a silicon mirror, which is optically coupled to the silicon waveguide;
a spot-size converter (SSC) comprised of a SSC material, which optically couples the RGM to the silicon waveguide, wherein the SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide;
wherein the RGM, the spot-size converter, the silicon waveguide and the silicon mirror collectively form a lasing cavity for the hybrid laser;
wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon; and
a laser output, which is optically coupled out of the lasing cavity.

2. The hybrid laser of claim 1 , wherein the lasing cavity includes a length l Si through silicon, a length l SSC through the SSC material and a length l OGM through the optical gain material;
wherein the effective refractive index of silicon is n Si , the effective refractive index of the SSC material is n SSC , and the effective refractive index of the optical gain material is n OGM ;
wherein the effective TOC of silicon is dn Si /dT, the effective TOC of the SSC material is dn SSC /dT, and the effective TOC of the optical gain material is dn OGM /dT; and
wherein l SSC ≈l OGM *(dn OGM /dT−dn Si /dT)/(dn Si /dT−dn SSC /dT), so that the effective TOC of the portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon.

3. The hybrid laser of claim 1 , wherein the silicon mirror comprises a micro-ring mirror.

4. The hybrid laser of claim 1 , wherein the silicon mirror comprises a distributed Bragg reflector (DBR).

5. The hybrid mirror of claim 1 , wherein the silicon mirror is a tunable silicon mirror, which includes a thermal-tuning mechanism.

6. The hybrid laser of claim 1 , wherein the RGM is located on a gain chip that is separate from a silicon photonic chip, which includes the silicon waveguide, and the silicon mirror.

7. The hybrid laser of claim 1 , wherein the spot-size converter is comprised of silicon oxynitride (SiON), wherein the nitrogen-to-oxygen ratio may vary.

8. The hybrid laser of claim 1 , wherein the spot-size converter is comprised of stoichiometric or low-stress silicon nitride (SiNx).

9. The hybrid laser of claim 1 , wherein the optical gain material is comprised of a III-V semiconductor.

10. A system, comprising:
at least one processor;
at least one memory coupled to the at least one processor; and
an optical transmitter for communicating optical signals generated by the system, wherein the optical transmitter includes a hybrid laser comprising:
a reflective gain medium (RGM) comprising an optical gain material coupled with an associated reflector;
a silicon waveguide;
a silicon mirror, which is optically coupled to the silicon waveguide;
a spot-size converter (SSC) comprised of a SSC material, which optically couples the RGM to the silicon waveguide, wherein the SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide;
wherein the RGM, the spot-size converter, the silicon waveguide and the silicon mirror collectively form a lasing cavity for the hybrid laser;
wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon; and
a laser output, which is optically coupled out of the lasing cavity.

11. The system of claim 10 , wherein the lasing cavity includes a length l Si through silicon, a length l SSC through the SSC material and a length l OGM through the optical gain material;
wherein the effective refractive index of silicon is n Si , the effective refractive index of the SSC material is n SSC , and the effective refractive index of the optical gain material is n OGM ;
wherein the effective TOC of silicon is dn Si /dT, the effective TOC of the SSC material is dn SSC /dT, and the effective TOC of the optical gain material is dn OGM /dT; and
wherein l SSC ≈l OGM *(dn OGM /dT−dn Si /dT)/(dn Si /dT−dn SSC /dT), so that the effective TOC of the portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon.

12. The system of claim 10 , wherein the silicon mirror comprises a micro-ring mirror.

13. The system of claim 10 , wherein the silicon mirror comprises a distributed Bragg reflector (DBR).

14. The system of claim 10 , wherein the silicon mirror is a tunable silicon mirror, which includes a thermal-tuning mechanism.

15. The system of claim 10 , wherein the RGM is located on a gain chip that is separate from a silicon photonic chip, which includes the silicon waveguide, and the silicon mirror.

16. The system of claim 10 , wherein the spot-size converter is comprised of silicon oxynitride (SiON), wherein the nitrogen-to-oxygen ratio may vary.

17. The system of claim 10 , wherein the spot-size converter is comprised of stoichiometric or low-stress silicon nitride (SiNx).

18. The system of claim 10 , wherein the optical gain material is comprised of a III-V semiconductor.

19. A method for operating a hybrid laser, comprising:
generating an optical signal by powering a reflective gain medium (RGM) comprising an optical gain material coupled with an associated reflector;
channeling the optical signal through a spot-size converter (SSC) and into a silicon waveguide, wherein the SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide;
channeling an optical signal from the silicon waveguide into a silicon mirror, which reflects the optical signal back to the RGM to form a lasing cavity; and
optically coupling light from the lasing cavity, which comprises the RGM, the SSC, the optical waveguide, and the silicon mirror, into a laser output;
wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon.

20. The method of claim 19 , wherein the lasing cavity includes a length l Si through silicon, a length l SSC through the SSC material and a length l OGM through the optical gain material;
wherein the effective refractive index of silicon is n Si , the effective refractive index of the SSC material is n SSC , and the effective refractive index of the optical gain material is n OGM ;
wherein the effective TOC of silicon is dn Si /dT, the effective TOC of the SSC material is dn SSC /dT, and the effective TOC of the optical gain material is dn OGM /dT; and
wherein l SSC ≈l OGM *(dn OGM /dT−n Si /dT)/(dn Si /dT−dn SSC /dT), so that the effective TOC of the portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon.

Assignees

• Oracle Int Corp

Inventors

• Lee Jin-Hyoung
• Zheng Xuezhe
• Shubin Ivan
• Bovington Jock T
• Krishnamoorthy Ashok V

Classifications

• H01S5/06817

  Noise reduction · CPC title

• H01S3/105 Primary

  by controlling the mutual position or the reflecting properties of the reflectors of the cavity {, e.g. by controlling the cavity length}({H01S3/10076}, H01S3/13 take precedence) · CPC title

• H01S5/14

  External cavity lasers (H01S5/18 takes precedence; mode locking H01S5/065) · CPC title

• H01S5/125

  Distributed Bragg reflector [DBR] lasers · CPC title

• H01S5/1092

  Multi-wavelength lasing · CPC title