# US 2021/0278615 A1 · Evanescent coupling of photodiode with optical waveguide

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- Number: US 2021/0278615 A1
- Document ID: US20210278615A1
- Status: Published application
- Kind: A1
- Application number: 17/302,854
- Filed: 2021-05-13
- Published: 2021-09-09
- Earliest claimed: 2019-11-27
- Assignees: Cisco Technology, Inc.
- Applicants: Cisco Technology, Inc.
- Inventors: Prakash B. GOTHOSKAR; Vipulkumar K. PATEL; Soha NAMNABAT; Ravi S. TUMMIDI
- Web page: https://patentgrep.com/patent/US20210278615A1

## CPC

- G02B 6/4298: {coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers}
- G02B 6/12004: {Combinations of two or more optical elements}
- G02B 6/305: {and having an integrated mode-size expanding section, e.g. tapered waveguide}
- G02B 6/4203: {Optical features}
- H10F 30/2235: {the devices comprising Group IV amorphous materials}
- H10F 77/148: {Shapes of potential barriers}
- H10F 77/413: {directly associated or integrated with the devices, e.g. back reflectors (directly associated or integrated with photovoltaic cells H10F77/42)}
- G02B 6/1228: {Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305)}
- G02B 2006/12123: {Diode}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

Embodiments described herein include an apparatus comprising a semiconductor-based photodiode disposed on a semiconductor layer, and an optical waveguide spaced apart from the semiconductor layer and evanescently coupled with a depletion region of the photodiode. The photodiode may be arranged as a vertical photodiode or a lateral photodiode.

## Claims

### Claim 1

An apparatus comprising:
a lateral photodiode disposed on a semiconductor layer; and
an optical waveguide spaced apart from the lateral photodiode and top-coupled with a depletion region of the lateral photodiode.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the lateral photodiode is disposed on a surface of the semiconductor layer.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the depletion region is formed in an intrinsic region of the photodiode.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein the intrinsic region extends into a recess formed from a surface of the semiconductor layer.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein one or both of a p-type region and an n-type region of the lateral photodiode extends into the recess.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein the optical waveguide is a first optical waveguide, the apparatus further comprising:
a second optical waveguide evanescently coupled with the first optical waveguide.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein the second optical waveguide is arranged above the first optical waveguide.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein the optical waveguide comprises:
a straight waveguide section that extends parallel to the depletion region; and
a tapered section having a narrow portion coupled to the straight waveguide section, and a wide portion configured to receive an optical signal.

### Claim 9 (depends on 1)

The apparatus of claim 1,
wherein the lateral photodiode comprises a first region doped with a first conductivity type, and a second region doped with a second, different conductivity type, and
wherein the semiconductor layer comprises a third region arranged beneath the first region of the lateral photodiode and doped with the first conductivity type, and a fourth region arranged beneath the second region of the lateral photodiode and doped with the second conductivity type.

### Claim 10 (depends on 9)

The apparatus of claim 9,
wherein the lateral photodiode further comprises a first intrinsic region arranged between the first region and the second region, and
wherein the semiconductor layer comprises a second intrinsic region arranged beneath the first intrinsic region.

### Claim 11 (depends on 1)

The apparatus of claim 1,
wherein the lateral photodiode is formed of germanium, and
wherein the semiconductor layer is formed of silicon.

### Claim 12 (depends on 11)

The apparatus of claim 11, wherein the semiconductor layer comprises a silicon-on-insulator (SOI) layer.

### Claim 13

An apparatus comprising:
a semiconductor layer defining a recess from a top surface;
a lateral photodiode comprising:
a first region doped with a first conductivity type;
a second region doped with a second, different conductivity type; and
an intrinsic region extending into the recess; and
an optical waveguide spaced apart from the lateral photodiode and top-coupled with a depletion region of the lateral photodiode.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein the first region and the second region extend into the recess.

### Claim 15 (depends on 13)

The apparatus of claim 13, wherein the first region and the second region are formed in the semiconductor layer.

### Claim 16 (depends on 13)

The apparatus of claim 13,
wherein the semiconductor layer comprises a third region arranged beneath the first region of the lateral photodiode and doped with the first conductivity type, and a fourth region arranged beneath the second region of the lateral photodiode and doped with the second conductivity type, and
wherein the semiconductor layer comprises a second intrinsic region arranged beneath the intrinsic region of the lateral photodiode.

### Claim 17 (depends on 13)

The apparatus of claim 13,
wherein the intrinsic region is formed of germanium, and
wherein the semiconductor layer is formed of silicon.

### Claim 18 (depends on 17)

The apparatus of claim 17, wherein the semiconductor layer comprises a silicon-on-insulator (SOI) layer.

### Claim 19 (depends on 13)

The apparatus of claim 13, wherein the optical waveguide is a first optical waveguide, the apparatus further comprising:
a second optical waveguide evanescently coupled with the first optical waveguide.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein the second optical waveguide is arranged above the first optical waveguide.