OPTICAL MODULATOR

摘要

A technical problem related to a travelling-wave electrode type optical modulator which is formed with a light guide and a traveling-wave electrode formed on a substrate having the electro-optical effect includes improvement of the characteristics such as optical modulation bandwidth, drive voltage, and characteristic impedance of the travelling-wave electrode type optical modulator. To solve the problem, a structure of a ridge is optimized which is formed in such a manner that a part of the substrate at a region where a high-frequency electric signal propagating in the travelling-wave electrode has high field intensity is reduced in thickness by digging. Further, a buffer layer is formed on the substrate where the ridge is formed and a conductive layer is formed on the buffer layer. At least one part of the buffer layer in the direction of a normal line to a sidewall of the ridge is made smaller in thickness than at least one of the buffer layer portion at a dug area on the substrate and the buffer layer portion on the top of the ridge.