Facet optical coupler

Patent metadata

Field	Value
Publication number	US-9703038-B1
Application number	US-201514796678-A
Country	US
Kind code	B1
Filing date	Jul 10, 2015
Priority date	Jul 11, 2014
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

Techniques for forming a facet optical coupler to couple light at an edge of silicon substrate are described. The facet optical coupler includes a silicon substrate, a layer of second material disposed on the silicon substrate and in direct contact with the edge of the silicon substrate, and an undercut region disposed between a portion of the silicon substrate and the layer of second material. The undercut region is offset from the edge to provide mechanical integrity of the facet optical coupler to improve production of photonic integrated circuits having the facet optical coupler from a wafer.

First claim

What is claimed is:

1. A facet optical coupler comprising:
a silicon substrate having a first two-dimensional edge and a second two-dimensional edge opposite the first two-dimensional edge;
a layer of second material disposed on the silicon substrate and having a two-dimensional edge substantially co-planar with the first two-dimensional edge of the silicon substrate;
an undercut region in the silicon substrate, the undercut region being proximate to and offset from the first two-dimensional edge of the silicon substrate and being distal from the second two-dimensional edge of the silicon substrate; and
a waveguide embedded within the layer of second material and having an end positioned over the undercut region such that the waveguide only partially extends across the undercut region,
wherein the undercut region is closer to the first two-dimensional edge than the waveguide.

2. The facet optical coupler of claim 1 , wherein the silicon substrate further includes a surface, and the layer of second material is disposed on the surface of the silicon substrate.

3. The facet optical coupler of claim 2 , wherein the layer of second material is in contact with the silicon substrate at the first two-dimensional edge.

4. The facet optical coupler of claim 1 , wherein the undercut region extends beyond the layer of second material in a direction perpendicular to a direction of light propagation and parallel to an interface of the undercut region and the layer of second material.

5. The facet optical coupler of claim 4 , wherein a dimension of the undercut region that is both perpendicular to the direction of light propagation and parallel to the interface of the undercut region and the layer of second material is at least 10 microns.

6. The facet optical coupler of claim 1 , wherein a dimension of the undercut region that is both perpendicular to a direction of light propagation in the waveguide and perpendicular to an interface of the undercut region and the layer of second material is at least 2 microns.

7. The facet optical coupler of claim 1 , wherein the undercut region is offset from the first two-dimensional edge of the silicon substrate by at least 20 microns.

8. The facet optical coupler of claim 1 , wherein the layer of second material decreases in size taken in a direction moving from the first two-dimensional edge of the silicon substrate to the waveguide.

9. The facet optical coupler of claim 1 , wherein the layer of second material is a layer of dielectric material.

10. The facet optical coupler of claim 1 , wherein the layer of second material includes one or more of SiO 2 , SiON, and Si 3 N 4 .

11. The facet optical coupler of claim 1 , further comprising a cladding layer positioned on the layer of second material.

12. The facet optical coupler of claim 11 , wherein each of the cladding layer and the undercut region has a lower refractive index than the layer of second material.

13. The facet optical coupler of claim 1 , wherein the waveguide has a first portion overlapping the undercut region and a second portion not overlapping the undercut region, and wherein the waveguide increases in size moving in a direction from the first portion to the second portion.

14. A method of manufacturing a facet optical coupler, the method comprising:
forming, in a surface of a silicon substrate having a first index of refraction, a region having a second index of refraction less than the first index of refraction, wherein the silicon substrate comprises a first two-dimensional edge and a second two-dimensional edge opposite the first two-dimensional edge, and wherein forming the region having the second index of refraction comprises forming the region having the second index of refraction proximate to and offset from the first two-dimensional edge of the silicon substrate and distal from the second two-dimensional edge of the silicon substrate;
forming a layer of second material on the surface of the silicon substrate such that an edge of the layer of second material is substantially co-planar with the first two-dimensional edge of the silicon substrate; and
forming a waveguide embedded in the layer of second material, wherein the waveguide has an end positioned over the region having the second index of refraction such that the waveguide only partially extends across the region, and such that the region having the second index of refraction is closer to the first two-dimensional edge than the waveguide.

15. The method of claim 14 , wherein forming the region having the second index of refraction comprises positioning the region having the second index of refraction at an offset of at least 20 microns from the first two-dimensional edge of the silicon substrate.

16. The method of claim 14 , wherein forming the region having the second index of refraction comprises removing a portion of the silicon substrate and filling the portion with a filler material having the second index of refraction.

17. The method of claim 14 , further comprising forming a cladding layer disposed on the layer of second material, wherein the cladding layer has a lower index of refraction than the layer of second material.

18. The method of claim 14 , wherein forming the region having the second index of refraction comprises forming the region having the second index of refraction to extend beyond the layer of second material in a direction perpendicular to a direction of light propagation in the waveguide and parallel to an interface of the region having the second index of refraction and the layer of second material, wherein a dimension of the region having the second index of refraction in the direction perpendicular to the direction of light propagation in the waveguide is at least 10 microns.

19. The method of claim 14 , wherein forming the layer of second material comprises forming the layer of second material with a decreasing size taken in a direction moving from the first two-dimensional edge of the silicon substrate to the waveguide.

20. The method of claim 14 , wherein forming the waveguide comprises forming the waveguide with a first portion overlapping the region having the second index of refraction and a second portion not overlapping the region having the second index of refraction, and wherein the waveguide increases in size moving in a direction from the first portion to the second portion.

21. A facet optical coupler comprising:
a silicon substrate having a facet coupling edge;
a layer of second material disposed on the silicon substrate and in contact with the silicon substrate at the facet coupling edge;
an undercut region disposed between a portion of the silicon substrate and the layer of second material and offset from the facet coupling edge; and
a waveguide embedded within the layer of second material, wherein the waveguide has an end proximate to the facet coupling edge, and the end is positioned over the undercut region such that the waveguide only partially extends across the undercut region,
wherein the undercut region is closer to the facet coupling edge than the waveguide.

Assignees

• Acacia Communications Inc

Inventors

• Chen Long

Classifications

• G02B6/24

  Coupling light guides · CPC title

• G02B6/14

  Mode converters · CPC title

• G02B2006/12097

  Ridge, rib or the like · CPC title

• G02B6/1228 Primary

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

• G02B6/305 Primary

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