Optical modulator, optical modulator module, and optical transmitter module

Patent metadata

Field	Value
Publication number	US-10754179-B2
Application number	US-201916515573-A
Country	US
Kind code	B2
Filing date	Jul 18, 2019
Priority date	Jul 31, 2018
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

An optical modulator includes an optical waveguide of a ridge type formed of a thin film of a dielectric material having an electro-optic effect over a substrate, a buffer layer covering the optical waveguide, and a signal electrode provided over the optical waveguide via the buffer layer, wherein a width of the signal electrode is greater than a ridge width of the optical waveguide and wherein the signal electrode covers at least one of sidewalls of a ridge of the optical waveguide.

First claim

What is claimed is:

1. An optical modulator comprising:
an optical waveguide of a ridge type formed of a thin film of a dielectric material having an electro-optic effect over a substrate;
a buffer layer covering the optical waveguide; and
a signal electrode provided over the optical waveguide via the buffer layer,
wherein a width of the signal electrode is greater than a ridge width of the optical waveguide and wherein the signal electrode covers at least one of sidewalls of a ridge of the optical waveguide, and
wherein the signal electrode covers, via the buffer layer, both sidewalls of the ridge of the optical waveguide symmetrically or asymmetrically with respect to a center in a width direction of the ridge.

2. An optical modulator comprising:
an optical waveguide of a ridge type formed of a thin film of a dielectric material having an electro-optic effect over a substrate;
a buffer layer covering the optical waveguide;
a signal electrode provided over the optical waveguide via the buffer layer; and
a ground electrode provided over the thin film at a predetermined distance from the signal electrode,
wherein a width of the signal electrode is greater than a ridge width of the optical waveguide and wherein the signal electrode covers at least one of sidewalls of a ridge of the optical waveguide, and
wherein the thin film located under the ground electrode has a terrace protruding toward the optical waveguide from a sidewall of the ground electrode.

3. The optical modulator as claimed in claim 1 ,
wherein the optical waveguide includes a first waveguide and a second waveguide that form a Mach-Zehnder interferometer,
wherein the signal electrode includes a first signal electrode provided to the first waveguide and a second signal electrode provided to the second waveguide, and
wherein a space between centers of the first signal electrode and the second signal electrode is greater than a space between ridge centers of the first waveguide and the second waveguide.

4. An optical modulator comprising:
an optical waveguide of a ridge type formed of a thin film of a dielectric material having an electro-optic effect over a substrate;
a buffer layer covering the optical waveguide; and
a signal electrode provided over the optical waveguide via the buffer layer,
wherein a width of the signal electrode is greater than a ridge width of the optical waveguide and wherein the signal electrode covers at least one of sidewalls of a ridge of the optical waveguide,
wherein the optical waveguide includes a first waveguide and a second waveguide that form a Mach-Zehnder interferometer,
wherein the signal electrode includes a first signal electrode provided to the first waveguide and a second signal electrode provided to the second waveguide,
wherein a space between centers of the first signal electrode and the second signal electrode is greater than a space between ridge centers of the first waveguide and the second waveguide,
wherein the first signal electrode covers an outer sidewall of a first ridge of the first waveguide with respect to a center axis of the Mach-Zehnder interferometer, and aligns with a surface of the buffer layer at an inner sidewall of the first ridge, and
wherein the second signal electrode covers an outer sidewall of a second ridge of the second waveguide with respect to the center axis of the Mach-Zehnder interferometer, and aligns with the surface of the buffer layer at an inner sidewall of the second ridge.

5. The optical modulator as claimed in claim 2 ,
wherein the optical waveguide includes a first waveguide and a second waveguide that form a Mach-Zehnder interferometer,
wherein the signal electrode includes a first signal electrode provided to the first waveguide and a second signal electrode provided to the second waveguide, and
wherein the ground electrode includes a first ground electrode provided at an outer side of the first signal electrode and a second ground electrode provided at an outer side of the second signal electrode, with respect to a center axis of the Mach-Zehnder interferometer.

6. The optical modulator as claimed in claim 5 , wherein the thin film located under the first ground electrode has a first terrace protruding toward the first waveguide and the thin film located under the second ground electrode has a second terrace protruding toward the second waveguide.

7. The optical modulator as claimed in claim 5 , further comprising:
a third ground electrode provided between the first signal electrode and the second signal electrode.

8. The optical modulator as claimed in claim 6 , further comprising:
a third ground electrode provided between the first signal electrode and the second signal electrode.

9. The optical modulator as claimed in claim 1 , wherein the substrate has a refractive index lower than a refractive index of the thin film.

10. The optical modulator as claimed in claim 1 , further comprising:
a second buffer layer provided between the substrate and the thin film.

11. An optical modulator module comprising:
an optical modulator having an optical waveguide of a ridge type formed of a thin film of a dielectric material having an electro-optic effect over a substrate, a buffer layer covering the optical waveguide, and a signal electrode provided over the optical waveguide via the buffer layer; and
a package to accommodate the optical modulator,
wherein a width of the signal electrode of the optical modulator is greater than a ridge width of the optical waveguide and wherein the signal electrode of the optical modulator covers at least one of sidewalls of a ridge of the optical waveguide, and
wherein the signal electrode covers, via the buffer layer, both sidewalls of the ridge of the optical waveguide symmetrically or asymmetrically with respect to a center in a width direction of the ridge.

12. The optical modulator module as claimed in claim 11 , further comprising:
a driver circuit provided in the package and electrically connected to the signal electrode of the optical modulator.

13. An optical transmitter module comprising:
the optical modulator as claimed in claim 1 ;
a light source configured to output light to be input to the optical modulator; and
a driver circuit configured to drive the optical modulator.

14. An optical transmitter module comprising:
the optical modulator as claimed in claim 2 ;
a light source configured to output light to be input to the optical modulator; and
a driver circuit configured to drive the optical modulator.

15. An optical transmitter module comprising:
the optical modulator as claimed in claim 4 ;
a light source configured to output light to be input to the optical modulator; and
a driver circuit configured to drive the optical modulator.

Assignees

• Fujitsu Optical Components Ltd

Inventors

• Ohmori Yasuhiro
• Kubota Yoshinobu
• Doi Masaharu
• Takeuchi Shintaro
• Yoshida Yoshihiko

Classifications

• G02F1/212

  Mach-Zehnder type · CPC title

• G02F1/035 Primary

  in an optical waveguide structure · CPC title

• G02F2202/20

  LiNbO3, LiTaO3 · CPC title

• G02B2006/12097

  Ridge, rib or the like · CPC title

• G02F2201/12

  electrode · CPC title