Optical coupling for whispering-gallery-mode resonators via waveguide gratings

• US 20050147355A1
• Filed: 07/06/2004
• Published: 07/07/2005
• Est. Priority Date: 07/03/2003
• Status: Active Grant

• Current Assignee: Oewaves Incorporated
• Original Assignee: Oewaves Incorporated
• Inventors: Ilchenko, Vladimir
• Granted Patent: US 7,062,131 B2
• Time in Patent Office: Days
• US Class Current: 385/50
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• 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

Abstract

This application describes whispering gallery modes resonators that are optically coupled to one or two waveguide grating couplers formed on a substrate.

Claims

1. A device, comprising:

a first waveguide having a first expanded section that has a first diffractive grating;

a second waveguide having a second expanded section that has a second diffractive grating, wherein the second expanded section is located adjacent to and is separated from the first expanded section and is not optically coupled to each other; and

an optical resonator located near the first and second expanded sections and optically coupled to the first and second waveguides via the first and the second diffractive gratings, respectively,

wherein the optical resonator supports whispering gallery modes and is in resonance with the first and the second diffractive gratings.

2. A device as in claim 1, wherein the optical resonator is a silica micro resonator.

3. A device as in claim 1, wherein the optical resonator is a sapphire micro resonator.

4. A device as in claim 1, wherein the optical resonator is a lithium niobate micro resonator.

5. A device as in claim 1, where the first and second waveguides, and the optical resonator are configured to make a wavelength of the whispering gallery mode to be between 0.5 micron to 3 microns.

6. A device as in claim 1, wherein a width of the first and second expanded sections is from 2 to 10 microns for light at a wavelength of 1550 nm.

7. A device as in claim 1, wherein the first and the second waveguides comprise Si.

8. A device as in claim 1, wherein the first and the second waveguides comprise InP.

9. A device as in claim 1, wherein the first expanded section includes a corrugated surface to effectuate the first diffractive grating.

10. A device as in claim 1, further comprising a substrate on which the first and the second waveguides are formed.

11. A device as in claim 1, wherein the first and second waveguides are arranged relative to each other in a counter-directional configuration and have a common grating period.

12. A device as in claim 1, wherein the first and second waveguides are arranged relative to each other in a co-directional configuration and have different grating periods.

13. A device, comprising:

a waveguide;

a waveguide mode expander having a tapered shape with a narrow end coupled to one end of the waveguide and a broad end; and

an expanded section coupled to the broad end of the waveguide mode expander and having a periodic grating structure in an elliptical shape.

14. A device as in claim 13, wherein the grating structure comprises grating grooves whose groove depths change along the direction of the grating structure.

15. A device as in claim 14, wherein the elliptical shape and the groove depths of the grating structure form a two-dimensional Gaussian profile.

16. A device as in claim 15, further comprising a whispering gallery mode resonator located near the grating structure to optically couple an evanescent field of a mode of the resonator to the grating structure.

17. A device as in claim 16, wherein the elliptical shape of the grating structure coincides with a spatial profile of the evanescent field of the mode of the resonator at the grating structure.

18. A device as in claim 13, further comprising:

a second waveguide;

a second waveguide mode expander having a tapered shape with a narrow end coupled to one end of the second waveguide and a broad end; and

a second expanded section coupled to the broad end of the second waveguide mode expander and having a second periodic grating structure in an elliptical shape,

wherein the second expanded section is located close to the expanded section of the waveguide.

19. A device as in claim 18, wherein each grating structure comprises grating grooves whose groove depths change along the direction of the grating structure.

20. A device as in claim 18, further comprising a whispering gallery mode resonator located near the expanded and the second expanded sections to optically couple an evanescent field of a mode of the resonator to the waveguide and the second waveguide.

21. A device as in claim 20, wherein the grating structure of the waveguide and the grating structure of the second waveguide are shaped to have a combined profile which coincides with a spatial profile of the evanescent field of the mode of the resonator at the grating structures.

22. A device as in claim 18, wherein said second periodic grating structure has a grating period different from a grating period of the grating structure.