# US 2017/0285265 A1 · Facet optical coupler

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2017/0285265 A1
- Document ID: US20170285265A1
- Status: Published application
- Kind: A1
- Application number: 15/620,601
- Filed: 2017-06-12
- Published: 2017-10-05
- Earliest claimed: 2014-07-11
- Assignees: Acacia Communications, Inc.
- Applicants: Acacia Communications, Inc.
- Inventors: Long Chen
- Web page: https://patentgrep.com/patent/US20170285265A1

## CPC

- G02B 6/1228: {Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305)}
- G02B 6/122: Basic optical elements, e.g. light-guiding paths
- G02B 6/14: Mode converters
- G02B 6/24: Coupling light guides
- G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide}
- G02B 2006/12097: {Ridge, rib or the like}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## 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.

## Claims

### Claim 1

A facet optical coupler comprising:
a substrate having opposing first and second two-dimensional edges;
an undercut region in the substrate, the undercut region being proximate to and offset from the first two-dimensional edge of the substrate and being distal from the second two-dimensional edge of the substrate; and
a waveguide having an end over the undercut region,
wherein the undercut region is closer to the first two-dimensional edge than is the end of the waveguide.

### Claim 2 (depends on 1)

The facet optical coupler of claim 1, wherein the substrate further includes a surface, and the facet optical coupler further comprises a layer of second material disposed on the surface of the substrate, wherein the waveguide is embedded in the layer of second material.

### Claim 3 (depends on 2)

The facet optical coupler of claim 2, wherein the layer of second material has a surface substantially co-planar with the first two-dimensional edge.

### Claim 4 (depends on 2)

The facet optical coupler of claim 2, wherein the undercut region extends beyond the layer of second material in a direction perpendicular to a direction of the waveguide.

### Claim 5 (depends on 2)

The facet optical coupler of claim 2, wherein a dimension of the undercut region that is parallel to an interface of the undercut region and the layer of second material is at least 10 microns.

### Claim 6 (depends on 2)

The facet optical coupler of claim 2, wherein a dimension of the undercut region that is perpendicular to an interface of the undercut region and the layer of second material is at least 2 microns.

### Claim 7 (depends on 2)

The facet optical coupler of claim 2, wherein the layer of second material decreases in size in a direction moving from the first two-dimensional edge of the substrate to the waveguide.

### Claim 8 (depends on 2)

The facet optical coupler of claim 2, wherein the second material is a dielectric material.

### Claim 9 (depends on 2)

The facet optical coupler of claim 2, wherein the second material includes one or more of SiO2, SiON, and Si3N4.

### Claim 10 (depends on 2)

The facet optical coupler of claim 2, further comprising a cladding layer on the layer of second material.

### Claim 11 (depends on 10)

The facet optical coupler of claim 10, wherein each of the cladding layer and the undercut region has a lower refractive index than the second material.

### Claim 12 (depends on 1)

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

### Claim 13 (depends on 1)

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.

### Claim 14

A method of manufacturing a facet optical coupler, the method comprising:
forming a region in a substrate such that the region has a lower index of refraction than the substrate and is positioned proximate to but offset from a first planar edge of the substrate and distal a second planar edge of the substrate opposite the first planar edge; and
forming a waveguide terminating over the region such that a distance between the waveguide and the first planar edge is greater than a distance between the region and the first planar edge.

### Claim 15 (depends on 14)

The method of claim 14, wherein forming the region comprises positioning the region at an offset of at least 20 microns from the first planar edge of the substrate.

### Claim 16 (depends on 14)

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

### Claim 17 (depends on 14)

The method of claim 14, further comprising forming a layer of second material over the substrate and forming a cladding layer on the layer of second material, wherein the waveguide is embedded in the layer of second material and the cladding layer has a lower index of refraction than the layer of second material.

### Claim 18 (depends on 17)

The method of claim 17, wherein forming the region comprises forming the region to extend beyond the layer of second material in a direction perpendicular to a direction of the waveguide.

### Claim 19 (depends on 17)

The method of claim 17, wherein forming the layer of second material comprises forming the layer of second material with a decreasing size in a direction moving from the first planar edge of the substrate to the waveguide.

### Claim 20 (depends on 14)

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