Patent ID: 7606447
Filing Date: 2009-10-20
Classification: G02B,G02F

Abstract:
1. A Mach-Zehnder type semiconductor device comprising a waveguide layer formed on one of principal surfaces of a semiconductor substrate having a first conductive type, a semiconducting layer having a second conductive type formed on said waveguide layer, and a common electrode formed on an other of the principal surfaces of said semiconductor substrate, said other of the principal surfaces being opposite to said one of the principal surfaces, said waveguide layer including an entrance waveguide for guiding propagation of an incident light entered from outside of said Mach-Zehnder type semiconductor device, an optical splitter connected to said entrance waveguide, for splitting said incident light into a first split light and a second split light, a first branch waveguide connected to said optical splitter, for guiding propagation of said first split light, a second branch waveguide connected to said optical splitter, for guiding propagation of said second split light, an optical coupler connected to said first branch waveguide and said second branch waveguide, for recombining said first split light and said second split light so as to produce an output light, and an exit waveguide connected to said optical coupler, for guiding propagation of said output light so as to cause said output light to emit from said Mach-Zehnder type semiconductor device, further comprising: a modulation electrode provided above said first branch waveguide, for changing a refraction index of said first branch waveguide by applying a modulated voltage across said modulation electrode and said common electrode; and a phase adjusting electrode group including a first negative bias electrode, a positive bias electrode, and a second negative bias electrode, which are provided above said second branch waveguide in sequence in a direction of propagation of said second split light and separated from each other, said positive bias electrode for changing a refraction index of said second branch waveguide by applying a positive bias voltage at said positive bias electrode relative to said common electrode so as to inject carriers into said second branch waveguide, said first and second negative bias electrodes for removing said carriers from said second branch waveguide to said semiconducting layer by applying a first negative bias voltage at said first negative bias electrode relative to said common electrode, and a second negative bias voltage at said second negative bias electrode relative to said common electrode.