Mach-Zehnder interferometer type optical modulator

A Mach-Zehnder interferometer type optical modulator comprising:

• a first optical waveguide and a second optical waveguide;
• an input optical coupler optically connected to one end of each of the first and second optical waveguides;
• an output optical coupler optically connected to the other end of each of the first and second optical waveguides;
• and
• a phase shifting section disposed between the input optical coupler and the output optical coupler,
• wherein the phase shifting section constitutes part of the first optical waveguide and part of the second optical waveguide and includes a first optical waveguide structure and a second optical waveguide structure each including an n-type semiconductor section, a core layer on the n-type semiconductor section, and a cladding layer on the core layer,
• the cladding layer of the first optical waveguide structure includes a first section disposed on the core layer of the first optical waveguide structure, and a second section and a third section disposed on the first section, the second section and the third section being juxtaposed to each other in a direction that intersects a waveguiding direction of the first optical waveguide structure,
• the cladding layer of the second optical waveguide structure includes a fourth section disposed on the core layer of the second optical waveguide structure, and a fifth section and a sixth section disposed on the fourth section, the fifth section and the sixth section being juxtaposed to each other in a direction that intersects a waveguiding direction of the second optical waveguide structure, and
• the first section, the second section, the fourth section, and the fifth section are composed of a p-type semiconductor, and the third section and the sixth section are composed of an undoped semiconductor.