Patent ID: 7039078

Claim:
A semiconductor optical modulator comprising at least: a lower cladding layer of a first conductivity type; a light absorption layer which is formed on said lower cladding layer and has a quantum-well structure constituted by a quantum-well layer and a barrier layer; and an upper cladding layer of a second conductivity type formed on said light absorption layer, wherein the quantum-well layer is made of In 1-x-y Ga x Al y N (0≦x, y≦1, 0≦x+y≦1), the barrier layers is made of In 1-x′-y′ Ga x′ Al y′ N (0≦x′, y′≦1, 0≦x′+y′≦1), an optical waveguide having a light incident end is constituted by said lower cladding layer, said light absorption layer, and said upper cladding layer, polarization is produced in the light absorption layer in the absence of a bias, and the light absorption layer is depleted by the polarization and a p-n junction built-in voltage such that the modulator is modulating light by depleting light absorption layer.