Optical modulator, method of achieving velocity matching and impedance matching of optical modulator, and method of manufacturing optical modulator

A method of achieving velocity matching and impedance matching of an optical modulator, comprising the steps of:

• preparing an optical modulation device having a substrate made of material having an electro-optic effect and a dielectric constant ∈LN, an optical waveguide disposed in said substrate, and modulating electrodes disposed on a principal surface of the substrate for applying a modulating signal to a lightwave guided through said optical waveguide;
• forming a dielectric layer having a first surface in contact with a reverse surface of said substrate;
• and
• forming a supporting substrate disposed on a second surface of said dielectric layer and having a recess at a position corresponding to at least a modulating region of said optical modulation device, wherein the relationship:
• ∈r>∈s is satisfied where ∈r represents the dielectric constant of said supporting substrate and ∈s represents the dielectric constant of solid, liquid, or gaseous substance in said recess.

A method of manufacturing an optical modulator, comprising the steps of:

• preparing an optical modulation device having a substrate made of material having an electro-optic effect and a dielectric constant ∈LN, an optical waveguide disposed in said substrate, and modulating electrodes disposed on a principal surface of the substrate for applying a modulating signal to a lightwave guided through said optical waveguide;
• forming a dielectric layer having a first surface in contact with a reverse surface of said substrate;
• and
• forming a supporting substrate disposed on a second surface of said dielectric layer and having a recess at a position corresponding to at least a modulating region of said optical modulation device, wherein the relationship:
• ∈r>∈s is satisfied where ∈r represents the dielectric constant of said supporting substrate and ∈s represents the dielectric constant of solid, liquid, or gaseous substance in said recess.