# US 8,541,050 B2 · Method for manufacturing optical waveguide

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- Number: US 8,541,050 B2
- Document ID: US8541050B2
- Status: Granted
- Kind: B2
- Application number: 12/988,401
- Filed: 2009-04-20
- Published: 2011-02-10
- Granted: 2013-09-24
- Earliest claimed: 2008-04-24
- Assignees: Panasonic Corporation
- Applicants: Tohru Nakashiba; Shinji Hashimoto; Naoyuki Kondou
- Inventors: Tohru Nakashiba; Shinji Hashimoto; Naoyuki Kondou
- Web page: https://patentgrep.com/patent/US8541050B2

## CPC

- G02B 6/138: by using polymerisation
- G02B 6/1221: {made from organic materials}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An object is to manufacture an optical waveguide having low optical loss, by smoothing the surface of a core. To this end, a method for manufacturing an optical waveguide includes: a core-forming layer formation step of forming a core-forming layer of a photosensitive polymer on a surface of a lower cladding layer formed on a substrate; a smoothing step of smoothing the surface by lowering a surface viscosity thereof through a heat treatment of the core-forming layer; and a photocuring step of forming a core through selective exposure of the smoothed core-forming layer.

## Claims

### Claim 1

A method for manufacturing an optical waveguide, the method comprising:
forming a core-forming layer of a photosensitive polymer on a lower cladding layer formed on a substrate;
smoothing the surface of the core-forming layer by lowering the surface viscosity thereof through a heat treatment of the core-forming layer to obtain a viscosity of the photosensitive polymer ranging from 5 to 10000 Pa·sec; and
forming a core through selective exposure to the core-forming layer from the surface of the smoothed core-forming layer.

### Claim 2 (depends on 1)

The method for manufacturing an optical waveguide according to claim 1, wherein the heat treatment is a treatment of smoothing the surface of the core-forming layer by softening the surface by heat.

### Claim 3 (depends on 1)

The method for manufacturing an optical waveguide according to claim 1, wherein the heat treatment is a treatment of smoothing the surface of the core-forming layer by melting the surface by heat.

### Claim 4 (depends on 1)

The method for manufacturing an optical waveguide according to claim 1,
wherein heat treatment conditions in the smoothing include a temperature such that a viscosity of the photosensitive polymer is 13 to 1800 Pa·sec.

### Claim 5 (depends on 1)

The method for manufacturing an optical waveguide according to claim 1,
wherein the photosensitive polymer is a photocurable polymer.

### Claim 6 (depends on 5)

The method for manufacturing an optical waveguide according to claim 5, wherein the photocurable polymer contains a bisphenol type epoxy resin and a photo-cationic curing agent.

### Claim 7 (depends on 1)

The method for manufacturing an optical waveguide according to claim 1,
wherein the core-forming layer formation bonds a film of the photosensitive polymer, which is formed beforehand, to the surface of the lower cladding layer.

### Claim 8 (depends on 7)

The method for manufacturing an optical waveguide according to claim 7, wherein the film is a film formed of a semi-cured photocurable polymer.

### Claim 9 (depends on 7)

The method for manufacturing an optical waveguide according to claim 7,
wherein the film is protected beforehand by a protective film, and is subjected to the heat treatment after stripping of the protective film.