GRATING-COUPLER ASSEMBLY WITH SMALL MODE-FIELD DIAMETER FOR PHOTONIC-INTEGRATED-CIRCUIT SYSTEMS

• US 20150309261A1
• Filed: 04/29/2014
• Published: 10/29/2015
• Est. Priority Date: 04/29/2014
• Status: Active Grant

• Current Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Original Assignee: Corning Optical Communications LLC (Corning Incorporated)
• Inventors: Zakharian, Aramais, Kobyakov, Andrey, Kuchinsky, Sergey Anatol'evich, Liu, Xue
• Granted Patent: US 9,453,969 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 6/04 formed by bundles of fibres G02B6/24 takes precedence
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence

Abstract

A grating-coupler assembly with a small mode-field diameter for photonic-integrated-circuit systems is disclosed. The assembly includes a silicon waveguide supported by a silicon-on-insulator substrate, and a grating coupler supported by the substrate and optically coupled to the silicon waveguide. The assembly has an optical fiber with a mode-field diameter in the range from 5 μm to 6 μm. One end of the optical fiber is disposed adjacent the grating coupler to define a coupling efficiency of 0.7 or greater.

Claims

1. A grating-coupler assembly for optically coupling light into or out of a photonic integrated circuit (PIC), comprising:

a silicon-on-insulator (SOI) substrate;

at least one silicon waveguide supported by the SOI substrate;

at least one grating coupler supported by the SOI substrate and optically coupled to the at least one silicon waveguide;

an optical fiber having an end and at least one core having a mode-field diameter MFD₆₀ in the range 5 μ

m≦

MFD₆₀≦

6 μ

m, wherein the optical-fiber end is disposed adjacent the at least one grating coupler; and

wherein the at least one core of the optical fiber and the at least one grating coupler define a coupling efficiency CE≧

0.7.

2. The grating-coupler assembly according to claim 1, further comprising an intervening medium of refractive index n_m>

1 between the optical-fiber end and the grating coupler.

3. The grating-coupler assembly according to claim 2, wherein the intervening medium comprises either an epoxy or an index-matching gel.

4. The grating-coupler assembly according to claim 1, wherein the silicon waveguide is optically coupled to one or more PIC components on the PIC.

5. The grating-coupler assembly according to claim 1, wherein the optical fiber includes a tapered end portion that includes the optical-fiber end.

6. The grating-coupler assembly according to claim 1, wherein the optical fiber comprises multiple cores and wherein the at least one grating coupler comprises corresponding multiple grating couplers.

7. The grating-coupler assembly according to claim 1, wherein the at least one grating coupler has a coupler footprint that is reduced by at least 15% as compared to a grating-coupler footprint as defined by a single-mode fiber having a mode-field diameter MFD_C of nominally 10 μ

m.

8. The grating-coupler assembly according to claim 1, wherein the mode-field diameter MFD₆₀ is nominally 5.4 μ

m.

9. The grating-coupler assembly according to claim 1, wherein an area reduction ratio R ranges from 0.25 to about 0.35 compared to a grating-coupler footprint defined by a single-mode fiber having a mode field diameter MFD_C of about 10 μ

m.

10. A grating-coupler assembly for optically coupling light into or out of a photonic integrated circuit (PIC), comprising:

a silicon waveguide supported by a silicon-on-insulator (SOI) substrate;

a grating coupler supported by the SOI substrate and optically coupled to the silicon waveguide, the grating coupler having a coupler footprint;

an optical fiber having an end and at least one core having a mode-field diameter MFD₆₀ in the range 5 μ

m≦

MFD₆₀≦

6 μ

m, wherein the optical-fiber end is disposed adjacent the grating coupler, with an intervening medium of refractive index n_m>

1 between the optical-fiber end and the grating coupler;

wherein the at least one core of the optical fiber and the grating coupler define a coupling efficiency CE≧

0.7; and

wherein the coupler footprint is reduced by at least 10% from a coupler footprint defined by a single-mode optical fiber having a mode-field diameter of nominally 10 μ

m.

11. The grating-coupler assembly according to claim 10, wherein the silicon waveguide is optically coupled to one or more PIC components on the PIC.

12. The grating-coupler assembly according to claim 10, wherein the optical fiber includes a tapered end portion that includes the optical-fiber end.

13. A method of optically coupling light into a photonic integrated circuit (PIC) that includes at least one grating coupler optically coupled to at least one silicon waveguide, comprising:

transmitting light through at least one core of an optical fiber having an end, the at least one core defining a mode-field diameter MFD₆₀ for the transmitted light, wherein the mode-field diameter MFD₆₀ is in the range 5 μ

m≦

MFD₆₀≦

6 μ

m;

emitting the transmitted light from the optical-fiber end to the at least one grating coupler; and

directing the emitted light from the at least one grating coupler to the at least one silicon waveguide such that the optical coupling of light from the at least one core to the at least one silicon waveguide is accomplished with a coupling efficiency CE≧

0.7.

14. The method according to claim 13, further comprising transmitting the emitted light through an intervening medium of refractive index n_m>

1 that resides between the optical-fiber end and the at least one grating coupler.

15. The method according to claim 14, wherein the optical fiber comprises multiple cores, the at least one grating coupler comprises multiple grating couplers and wherein each core is optically coupled to one of the grating couplers.

16. The method according to claim 14, wherein the at least one grating coupler has a coupler footprint that is reduced by at least 15% as compared to a grating-coupler footprint as defined by a single-mode fiber having a mode-field diameter of nominally 10 μ

m.

17. A method of optically coupling light from a photonic integrated circuit (PIC) that includes at least one grating coupler optically coupled to at least one silicon waveguide, comprising:

transmitting light from the at least one silicon waveguide to the at least one grating coupler;

directing the transmitted light from the at least one grating coupler to at least one core of an optical fiber having an end arranged adjacent the at least one grating coupler, the at least one core defining a mode-field diameter MFD₆₀ for the transmitted light, wherein the mode-field diameter MFD₆₀ is in the range 5 μ

m≦

MFD₆₀≦

6 μ

m; and

wherein optical coupling of light from the at least one silicon waveguide to the at least one core is accomplished with a coupling efficiency CE≧

0.7.

18. The method according to claim 17, further comprising transmitting the light through an intervening medium of refractive index n_m>

1 that resides between the optical-fiber end and the at least one grating coupler.

19. The method according to claim 17, wherein the optical fiber comprises multiple cores, the at least one grating coupler comprises multiple grating couplers and wherein each core is optically coupled to one of the grating couplers.

20. The method according to claim 17, wherein the at least one grating coupler has a coupler footprint that is reduced by an amount by at least 15% as compared to a grating-coupler footprint as defined by a single-mode fiber having a mode-field diameter of nominally 10 μ

m.