Optical coupler having exposed subwavelength gratings for coupling electromagnetic field

Patent metadata

Field	Value
Publication number	US-10126500-B2
Application number	US-201715797528-A
Country	US
Kind code	B2
Filing date	Oct 30, 2017
Priority date	Nov 1, 2016
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

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.

First claim

The invention claimed is:

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 cladding 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.

Assignees

• Purdue Research Foundation

Inventors

• Qi Minghao
• Teng Min
• Han Kyunghun
• Kim Sangsik
• Niu Ben
• Lee Yun Jo

Classifications

• G02B6/305

  and having an integrated mode-size expanding section, e.g. tapered waveguide · CPC title

• G02B6/1228

  Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305) · CPC title

• G02B6/124 Primary

  Geodesic lenses or integrated gratings · CPC title

• G02B6/3636

  the mechanical coupling means being grooves (G02B6/3652 takes precedence) · CPC title

• G02B5/1809

  with pitch less than or comparable to the wavelength · CPC title