Patent ID: 8498501

Claim:
A semiconductor optical modulator comprising: a substrate; a first n-type cladding layer; a semiconductor optical modulation layer; a p-type cladding layer; a second n-type cladding layer; a passivation film; and an electric field-relaxing layer, wherein the first n-type cladding layer, the semiconductor optical modulation layer, the p-type cladding layer, and the second n-type cladding layer are laminated on the substrate in this order to form a waveguide structure, the passivation film is arranged at side surfaces of the waveguide structure, the electric field-relaxing layer is interposed between the p-type cladding layer and the second n-type cladding layer, and an impurity concentration of the electric field-relaxing layer is lower than that of the p-type cladding layer and that of the second n-type cladding layer.