# US 2026/0086397 A1 · Optical waveguide element, optical modulator, and optical transmission apparatus

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

- Number: US 2026/0086397 A1
- Document ID: US20260086397A1
- Status: Published application
- Kind: A1
- Application number: 19/312,282
- Filed: 2025-08-27
- Published: 2026-03-26
- Earliest claimed: 2024-09-26
- Assignees: Sumitomo Osaka Cement Co., Ltd.
- Applicants: Sumitomo Osaka Cement Co., Ltd.
- Inventors: Kosuke Okahashi
- Web page: https://patentgrep.com/patent/US20260086397A1

## CPC

- G02F 1/035: in an optical waveguide structure
- G02F 1/0356: {controlled by a high-frequency electromagnetic wave component in an electric waveguide structure}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

An optical waveguide element 1 according to the disclosure includes: a substrate 10 including electro-optic crystal and forming an optical waveguide 80; an electrode 60 placed on the substrate 10; an electrode underlayer 50 disposed in contact with a lower surface of the electrode 60; and an oxygen deficiency prevention layer 40 disposed in contact with at least a part of a lower surface of the electrode underlayer 50 and at least a part of an upper surface (substrate upper surface 10a) of the substrate 10, and preventing oxygen deficiency of the substrate 10.

## Claims

### Claim 1

An optical waveguide element, comprising:
a substrate comprising electro-optic crystal and forming an optical waveguide;
an electrode placed on the substrate;
an electrode underlayer disposed in contact with a lower surface of the electrode; and
an oxygen deficiency prevention layer disposed in contact with at least a part of a lower surface of the electrode underlayer and at least a part of an upper surface of the substrate, and preventing oxygen deficiency of the substrate due to the electrode underlayer.

### Claim 2 (depends on 1)

The optical waveguide element according to claim 1, wherein the oxygen deficiency prevention layer is disposed in contact with an entire surface of the lower surface of the electrode underlayer.

### Claim 3 (depends on 1)

The optical waveguide element according to claim 1, wherein the oxygen deficiency prevention layer is disposed below a DC electrode that applies a DC voltage.

### Claim 4 (depends on 1)

The optical waveguide element according to claim 1, wherein the oxygen deficiency prevention layer is disposed below the electrode having a thickness of 1.0 μm or less.

### Claim 5 (depends on 1)

The optical waveguide element according to claim 1, comprising a reinforcing substrate bonded below the substrate via a bonding layer,
wherein the substrate comprises an LN substrate having a thickness of 1.0 μm or less, and
a ridge portion used as the optical waveguide is formed on the upper surface of the substrate.

### Claim 6 (depends on 5)

The optical waveguide element according to claim 5, wherein the oxygen deficiency prevention layer is not formed on a surface of the ridge portion.

### Claim 7 (depends on 5)

The optical waveguide element according to claim 5, wherein an arithmetic mean roughness Ra of the surface of the ridge portion is 5.0 nm or less.

### Claim 8 (depends on 1)

The optical waveguide element according to claim 1, wherein the oxygen deficiency prevention layer comprises a material having a refractive index of 1.3 or more and a dielectric constant of 3.0 or more.

### Claim 9 (depends on 1)

The optical waveguide element according to claim 1, wherein a material constituting the oxygen deficiency prevention layer is SiO2, and an average atomic ratio of oxygen to silicon is greater than 1.9.

### Claim 10 (depends on 1)

The optical waveguide element according to claim 1, wherein a content ratio of inert gas in the oxygen deficiency prevention layer is 1.0 atm % to 3.0 atm %.

### Claim 11 (depends on 1)

The optical waveguide element according to claim 1, wherein a thickness of the oxygen deficiency prevention layer is 10 nm to 200 nm.

### Claim 12 (depends on 1)

An optical modulator, comprising:
the optical waveguide element according to claim 1;
a housing accommodating the optical waveguide element;
an input optical fiber connected to an optical input portion of the optical waveguide element; and
an output optical fiber connected to an optical output portion of the optical waveguide element.

### Claim 13 (depends on 12)

The optical modulator according to claim 12, comprising, as the electrode, a modulation electrode that modulates light waves propagating through the optical waveguide, and having a signal amplification circuit inside the housing, which amplifies a modulation signal applied to the modulation electrode.

### Claim 14 (depends on 13)

An optical transmission apparatus, comprising:
the optical modulator according to claim 13;
a light source inputting light waves to the optical modulator; and
a signal output circuit outputting the modulation signal.