# US 11,906,781 B2 · End-face coupling structures underneath a photonic layer

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- Number: US 11,906,781 B2
- Document ID: US11906781B2
- Status: Granted
- Kind: B2
- Application number: 18/064,506
- Filed: 2022-12-12
- Published: 2023-04-13
- Granted: 2024-02-20
- Earliest claimed: 2021-01-29
- Assignees: Cisco Technology, Inc.
- Applicants: Cisco Technology, Inc.
- Inventors: Roman Bruck; Gianlorenzo Masini
- Web page: https://patentgrep.com/patent/US11906781B2

## CPC

- G02B 6/136: by etching
- G02B 6/125: Bends, branchings or intersections
- G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide}
- G02B 6/12004: {Combinations of two or more optical elements}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A method includes providing a photonic wafer that includes an electrical layer and a layer disposed on a substrate. The layer includes at least one optical waveguide that is disposed between the electrical layer and the substrate. The method also includes removing a portion of the substrate underneath the at least one optical waveguide and forming an end-face coupler. A portion of the end-face coupler is within the removed portion of the substrate. The end-face coupler transmits an optical signal to, or receives an optical signal from, an external optical device.

## Claims

### Claim 1

An apparatus, comprising:
a photonic wafer comprising an electrical layer and a layer disposed on a substrate, wherein the layer comprises at least one optical waveguide that is disposed between the electrical layer and the substrate; and
an end-face coupler, wherein a portion of the end-face coupler is within a portion of the substrate underneath the at least one optical waveguide, and wherein the end-face coupler is configured to direct an optical signal to or from the optical waveguide and comprises an optical interface for end-face coupling.

### Claim 2 (depends on 1)

The apparatus of claim 1, further comprising through vias through the substrate, through the layer, and to the electrical layer.

### Claim 3 (depends on 1)

The apparatus of claim 1, further comprising a cladding disposed around the end-face coupler, wherein the end-face coupler comprises a first material that has a higher index of refraction than the cladding.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein the end-face coupler further comprises a stack on the first material, the stack comprising a plurality of different materials.

### Claim 5 (depends on 3)

The apparatus of claim 3, wherein the end-face coupler further comprises:
a first prong in the cladding, the first prong comprising a second material; and
a second prong formed by the first material.

### Claim 6

A method, comprising:
providing a photonic wafer comprising at least one optical waveguide disposed on a substrate;
removing a portion of the substrate underneath the at least one optical waveguide;
depositing a material in the removed portion of the substrate; and
patterning and etching the material to form an end-face coupler configured to transmit an optical signal from an external optical device to the at least one optical waveguide.

### Claim 7 (depends on 6)

The method of claim 6, further comprising forming a through via through the substrate.

### Claim 8 (depends on 6)

The method of claim 6, further comprising depositing a cladding over the end-face coupler, wherein the material has a higher index of refraction than the cladding.