Optical modulator

Abstract

Provided is an optical modulator in which even in a case where an optical waveguide and a control electrode are highly integrated, a distortion due to stress acting on the optical waveguide from lead-out wiring of a signal electrode is mitigated and occurrence of a temperature drift or the like is suppressed. An optical modulator includes: a substratehaving an electro-optic effect; optical waveguides (Lto L), each of which is formed on the substrate and provided with at least one Mach-Zehnder type optical waveguide; and a control electrode which controls light waves propagating through the optical waveguides, in which the control electrode is configured of signal electrodes (Sand S) and ground electrodes (Gto G), each of the signal electrodes being provided with a pad part (SP or SP) for input or output, which is electrically connected to an electric circuit which is provided outside the substrate, an interaction part (indicated by arrow R) which applies an electric field to the optical waveguide, and a lead-out wiring part which connects the pad part and the interaction part to each other, a portion of the lead-out wiring part is disposed parallel to an extended direction (a lateral direction in) of the Mach-Zehnder type optical waveguide within a range (indicated by arrow R) in which two branching waveguides configuring the Mach-Zehnder type optical waveguide are present in the extended direction, and any one of a portion of the interaction part, another portion of the lead-out wiring part, and a stress relaxation structure of the ground electrode is formed at a position which is axially symmetrical to the portion of the lead-out wiring part with respect to a centrosymmetric axis in the extended direction of the Mach-Zehnder type optical waveguide.