Patent ID: 6872966

Claim:
An optical semiconductor device comprising: a bias layer formed on a semiconductor substrate and made of a first conductivity type semiconductor; a first optical waveguide formed on the bias layer, and having a stripe-like first core layer that is put between a first upper clad layer and a first lower clad layer made of the first conductivity type semiconductor; a second optical waveguide formed on the bias layer to be put between a second upper clad layer, which is separated from the first upper clad layer, and a second lower clad layer made of the first conductivity type semiconductor, and having a stripe-like second core layer that is formed separately from the first core layer; a first phase modulation electrode formed on the first upper clad layer of the first optical waveguide; a second phase modulation electrode formed on the second upper clad layer of the second optical waveguide; a first slot-line electrode formed on a side of the first optical waveguide and connected to the first phase modulation electrode via a first air-bridge wiring; a second slot-line electrode formed on a side of the second optical waveguide and connected to the second phase modulation electrode via a second air-bridge wiring; a first optical coupler formed over the semiconductor substrate and connected to respective one ends of the first optical waveguide and the second optical waveguide; and a second optical coupler formed over the semiconductor substrate and connected to respective other ends of the first optical waveguide and the second optical waveguide.