Thermo-optic phase shifter for semiconductor optical waveguide

An apparatus comprising:

• an optical waveguide formed in a semiconductor layer and extending along a first axis, the optical waveguide having a first doping level;
• and
• a first contact region and a second contact region formed in the semiconductor layer apart from the first axis, wherein the first contact region and the second contact region each have a corresponding second doping level that is greater than the first doping level,
• wherein an electrical current is conducted through the optical waveguide along at least a first dimension of the optical waveguide responsive to a voltage signal applied between the first contact region and the second contact region, and
• wherein resistive heating of the optical waveguide is provided by the electrical current.

A method comprising:

• receiving, at a first end of an optical waveguide formed in a semiconductor layer and extending along a first axis, an optical signal having a first phase;
• and
• transmitting, at a second end of the optical waveguide opposite the first end, a modified optical signal having a second phase different than the first phase,
• wherein transmitting a modified optical signal comprises:
• applying a voltage signal between a first contact region and a second contact region formed in the semiconductor layer apart from the first axis, wherein applying a voltage signal causes an electrical current to be conducted through the optical waveguide along at least a first dimension of the optical waveguide, wherein the electrical current causes resistive heating of the optical waveguide and a desired phase shift between the first phase and the second phase.