Patent ID: 7474812
Filing Date: 2009-01-06
Classification: G02F

Abstract:
1. A monitor photodetector-equipped optical modulator comprising: an optical modulator having a substrate, an optical waveguide, a center electrode, and at least one ground electrode, wherein the substrate has an electro-optic effect, the optical waveguide guides a light beam and is formed on one surface side of the substrate, and the center electrode and the at least one ground electrode have a voltage applied therebetween for modulating the light beam guided by the optical waveguide, wherein the optical waveguide includes an input optical waveguide, two branching optical waveguides, two interaction optical waveguides, a multiplexing optical waveguide, and an output optical waveguide, wherein the light beam is incident on the optical waveguide through the input optical waveguide, the two branching optical waveguides guide the light beam incident on the input optical waveguide while branching the light beam into two light beams, the two interaction optical waveguides modulate each phase of the two light beams by applying the voltage between the center electrode and the at least one ground electrode, the multiplexing optical waveguide multiplexes the two light beams which propagate through the two interaction optical waveguides, and the output optical waveguide is connected to the multiplexing optical waveguide through a multiplexing point of the multiplexing optical waveguide which multiplexes the two light beams, and wherein a high-order mode light beam which is generated by multiplexing the phase-modulated two light beams in the multiplexing optical waveguide is radiated from the multiplexing point to inside the substrate as two radiant light beams while the high-order mode light beam does not substantially propagate through the output optical waveguide in the optical modulator; and a monitor photodetector which is disposed outside the substrate except on said one surface side of the substrate, and which detects at least one of the two radiant light beams radiated from the multiplexing point inside the substrate of the optical modulator, wherein the output optical waveguide of the optical modulator is formed while being deformed in order to secure a space for mounting the monitor photodetector such that at least one of optical axes of the radiant light beams in a substrate facet located on the output optical waveguide and an edge portion of the output optical waveguide are separated from each other by a predetermined distance.