OPTICAL COUPLER HAVING SUBWAVELENGTH GRATING

• US 20180120504A1
• Filed: 10/30/2017
• Published: 05/03/2018
• Est. Priority Date: 11/01/2016
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Qi, Minghao, Teng, Min, Han, Kyunghun, Kim, Sangsik, Niu, Ben, Lee, Yun Jo
• Granted Patent: US 10,126,500 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength
• 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 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide
• CPC Class Codes: G02B 6/3636 the mechanical coupling means being grooves G02B6/3652 takes precedence

Abstract

A semiconductor photonic device includes a substrate, facet(s), and optical coupler(s) associated with the facet(s). Each optical coupler can couple an electromagnetic field incident on the respective facet towards a buried waveguide as the electromagnetic field proceeds into the semiconductor photonic device. In some examples, each coupler has waveguides extending in a longitudinal direction and at least partly encapsulated within a cladding layer. In some examples, at least one waveguide tapers along its length. In some examples, at least one waveguide includes spaced-apart segments arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation.

Claims

1. An optical coupler, comprising:

a semiconductor substrate;

a first cladding layer arranged at least partly over the semiconductor substrate;

a second cladding layer arranged at least partly over the first cladding layer with respect to the semiconductor substrate;

a facet in the first cladding layer and in the second cladding layer, the facet extending substantially in a lateral direction; and

a plurality of waveguides arranged over the first insulating layer with respect to the semiconductor substrate,

wherein the plurality of waveguides comprises;

a first exposed waveguide comprising a plurality of first spaced-apart segments arranged substantially along a longitudinal direction;

a second exposed waveguide; and

a first buried waveguide; and

wherein at least two of the waveguides of the plurality of waveguides;

are at least partly encapsulated in the second cladding layer;

have respective refractive indices higher than a refractive index of the second cladding layer; and

are spaced apart from each other along the lateral direction.

2. The optical coupler according to claim 1, wherein:

the semiconductor substrate comprises crystalline silicon or a III-V semiconductor;

the first cladding layer comprises buried oxide;

the second cladding layer comprises silicon oxide;

or

at least one of the plurality of waveguides comprises silicon.

3. The optical coupler according to claim 1, wherein:

at least some of the first spaced-apart segments are arranged to form a subwavelength grating (SWG);

the at least some of the first spaced-apart segments have substantially equal extents in the lateral direction and in a third direction that is substantially perpendicular to both the lateral direction and the longitudinal direction;

the at least some of the first spaced-apart segments are spaced apart in the longitudinal direction substantially evenly;

the at least some of the first spaced-apart segments have substantially equal lengths (L) in the longitudinal direction; and

the at least some of the first spaced-apart segments are separated from each other by gaps extending in the longitudinal direction a distance substantially equal to a grating period (Λ

) minus the lengths L.

4. The optical coupler according to claim 1, wherein the first exposed waveguide is tapered along at least part of its length.

5. The optical coupler according to claim 1, wherein the first exposed waveguide has a substantially constant lateral extent along a portion of its length, the portion extending substantially in the longitudinal direction substantially from the facet.

6. The optical coupler according to claim 5, wherein the second exposed waveguide is tapered along a portion of its length, the portion of the length of the second exposed waveguide extending substantially from the facet.

7. The optical coupler according to claim 1, wherein the second exposed waveguide comprises a plurality of second spaced-apart segments arranged substantially along the longitudinal direction.

8. The optical coupler according to claim 7, wherein the second exposed waveguide is tapered along at least a portion of its length.

9. The optical coupler according to claim 7, wherein at least some of the second spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having a wavelength shorter than one hundred microns.

10. The optical coupler according to claim 9, wherein at least some of the first spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having the wavelength shorter than one hundred microns.

11. The optical coupler according to claim 1, wherein:

the plurality of waveguides further comprises a second buried waveguide;

the second buried waveguide comprises a plurality of third spaced-apart segments arranged substantially along the longitudinal direction;

a longitudinal axis of the second buried waveguide substantially coincides with a longitudinal axis of the first buried waveguide; and

the second buried waveguide is arranged longitudinally between the facet and the first buried waveguide.

12. The optical coupler according to claim 11, wherein the second buried waveguide is spaced apart longitudinally from the facet.

13. The optical coupler according to claim 11, wherein at least some of the third spaced-apart segments are arranged to form a subwavelength grating (SWG) configured to entrain electromagnetic radiation having a wavelength shorter than one hundred microns.

14. The optical coupler according to claim 1, wherein:

the semiconductor substrate comprises monocrystalline silicon;

the first insulating layer comprises buried oxide;

the second insulating layer comprises silicon oxide;

or

at least one waveguide of the plurality of waveguides comprises silicon nitride.

15. The optical coupler according to claim 1, further comprising an active unit optically connected with the first buried waveguide.

16. The optical coupler according to claim 1, wherein the first buried waveguide is tapered along at least part of its length.

17. An assembly comprising:

a semiconductor photonic device having;

a substrate;

a plurality of facets; and

a plurality of optical couplers associated with respective facets of the plurality of facets; and

a plurality of single-mode optical fibers disposed in a splice configuration with respect to respective facets of the plurality of facets;

wherein each optical coupler of the plurality of optical couplers comprises;

a respective buried waveguide; and

means for coupling an electromagnetic field incident on the facet towards the respective buried waveguide as the electromagnetic field proceeds into the semiconductor photonic device.

18. The assembly according to claim 17, further comprising a V-groove array configured to retain the single-mode optical fibers in position with respect to the respective facets.

19. The assembly according to claim 17, wherein each optical coupler comprises:

a respective first exposed waveguide; and

a respective second exposed waveguide;

wherein the respective first exposed waveguide, the respective buried waveguide, and the respective second exposed waveguide of each optical coupler are spaced apart in a lateral direction of that optical coupler; and

at least one of the respective first exposed waveguide, the respective buried waveguide, and the respective second exposed waveguide of each optical coupler comprises a plurality of segments spaced apart in a longitudinal direction of that optical coupler.

20. The assembly according to claim 17, wherein:

the semiconductor photonic device comprises a cladding layer; and

the respective first exposed waveguides and the respective second exposed waveguides;

are at least partly encapsulated in the cladding layer; and

have respective indices of refraction that are higher than an index of refraction of the cladding layer.