Optical modulator

Patent metadata

Field	Value
Publication number	US-10989980-B2
Application number	US-202016799753-A
Country	US
Kind code	B2
Filing date	Feb 24, 2020
Priority date	Feb 25, 2019
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

Abstract

An optical modulator is provided with a substrate, first and second optical waveguides each formed of a ridge-shaped electro-optic material film and disposed so as to be mutually adjacent on the substrate, a buffer layer covering upper surfaces of the first and second optical waveguides, first and second signal electrodes provided above the buffer layer so as to be opposed respectively to the first and second optical waveguides, and a dielectric layer covering at least one of a part of an exposed surface of the first signal electrode and a part of an exposed surface of the second signal electrode, and a part of an upper surface of the buffer layer. Differential signals are applied to the first and second signal electrodes.

First claim

What is claimed is:

1. An optical modulator comprising:
a substrate;
first and second optical waveguides each formed of a ridge-shaped electro-optic material film and disposed so as to be mutually adjacent on the substrate;
a buffer layer covering upper surfaces of the first and second optical waveguides;
an insulating layer formed above the buffer layer;
an electrode layer formed on the insulating layer and including first and second signal electrodes provided above the buffer layer so as to be opposed respectively to the first and second optical waveguides; and
a dielectric layer covering at least one of a part of an exposed surface of the first signal electrode and a part of an exposed surface of the second signal electrode, and a part of an upper surface of the buffer layer, wherein
the first signal electrode includes a first lower layer part opposed to the first optical waveguide through the buffer layer and a first upper layer part provided above the first lower layer part,
the second signal electrode includes a second lower layer part opposed to the second optical waveguide through the buffer layer and a second upper layer part provided above the second lower layer part,
a width of a lower surface of each of the first and second lower layer parts is smaller than a width of each of the first and second upper layer parts,
a width of the first upper layer part extends from the first lower layer part to a side opposite to the second signal electrode,
a width of the second upper layer part extends from the second lower layer part to the side opposite to the first signal electrode,
the first and second upper layer parts are formed in the electrode layer,
the first and second lower layer parts are each embedded in openings formed in the insulating layer, and
differential signals are applied to the first and second signal electrodes.

2. The optical modulator as claimed in claim 1 , wherein a gap between the first and second upper layer parts is equal to or larger than a gap between the first and second lower layer parts.

3. The optical modulator as claimed in claim 1 , wherein at least part of the insulating layer existing at the lower portion of an electrode isolation area between the first and second signal electrodes may be removed.

4. The optical modulator as claimed in claim 1 , wherein
the dielectric layer is formed on upper and side surfaces of each of the first and second signal electrodes and an upper surface of the insulating layer in an area not overlapping the first and second signal electrodes in a plan view.

5. The optical modulator as claimed in claim 1 , wherein
the dielectric layer is formed on the upper surface of the buffer layer, and
the insulating layer is formed on an upper surface of the dielectric layer.

6. The optical modulator as claimed in claim 1 , wherein no ground electrode is provided in an area in the vicinity of the first signal electrode on a side opposite to the second signal electrode with respect to the first signal electrode and in an area in the vicinity of the second signal electrode on a side opposite to the first signal electrode with respect to the second signal electrode.

7. An optical modulator comprising:
a substrate;
first and second optical waveguides each formed of a ridge-shaped electro-optic material film and disposed so as to be mutually adjacent on the substrate;
a buffer layer covering upper surfaces of the first and second optical waveguides;
first and second signal electrodes provided above the buffer layer so as to be opposed respectively to the first and second optical waveguides; and
a dielectric layer covering at least one of a part of an exposed surface of the first signal electrode and a part of an exposed surface of the second signal electrode, and a part of an upper surface of the buffer layer, wherein
a first ground electrode disposed in an area in the vicinity of the first signal electrode on a side opposite to the second signal electrode with respect to the first signal electrode; and
a second ground electrode disposed in an area in the vicinity of the second signal electrode on a side opposite to the first signal electrode with respect to the second signal electrode.

8. An optical modulator comprising:
a substrate;
first and second optical waveguides each formed of a ridge-shaped electro-optic material film and disposed so as to be mutually adjacent on the substrate;
a buffer layer covering upper surfaces of the first and second optical waveguides;
first and second signal electrodes provided above the buffer layer so as to be opposed respectively to the first and second optical waveguides; and
a dielectric layer covering at least one of a part of an exposed surface of the first signal electrode and a part of an exposed surface of the second signal electrode, and a part of an upper surface of the buffer layer, wherein
each of the first and second optical waveguides has at least one linear section and at least one curved section,
the first signal electrode is provided along the linear section and the curved section of the first optical waveguide, and
the second signal electrode is provided along the linear section and the curved section of the second optical waveguide.

9. An optical modulator comprising:
a substrate;
first and second optical waveguides each formed of a ridge-shaped lithium niobate film and disposed so as to be mutually adjacent on the substrate;
a buffer layer covering upper surfaces of the first and second optical waveguides;
first and second signal electrodes provided above the buffer layer so as to be opposed respectively to the first and second optical waveguides; and
a dielectric layer covering at least one of a part of an exposed surface of the first signal electrode and a part of an exposed surface of the second signal electrode, and a part of an upper surface of the buffer layer, wherein
a c-axis of the lithium niobate film is oriented perpendicular to a main surface of the substrate.

Assignees

• Tdk Corp
• Fujitsu Optical Components Ltd

Inventors

• Iwatsuka Shinji
• Endou Kenji
• Hara Hiroki
• Matsuura Toshinori
• Kikukawa Takashi
• Ohmori Yasuhiro
• Doi Masaharu
• Takeuchi Shintaro
• Tanaka Takehito
• Kubota Yoshinobu

Classifications

• G02F2202/20

  LiNbO3, LiTaO3 · CPC title

• G02F2201/07

  buffer layer · CPC title

• G02F1/2255 Primary

  controlled by a high-frequency electromagnetic component in an electric waveguide structure · CPC title

• G02F1/212

  Mach-Zehnder type · CPC title

• G02F2201/063

  ridge; rib; strip loaded · CPC title