LIGHT MODULATOR

摘要

PROBLEM TO BE SOLVED: To provide a light modulator arranging a light-receiving element on a substrate constituting the light modulator and capable of suppressing reduction of the frequency band of the light-receiving element even when two radiation beams from the multiplexing part of a Mach-Zehnder type optical waveguide are simultaneously received and monitored.SOLUTION: A light modulator comprises: a substrate 1; an optical waveguide including a Mach-Zehnder type optical waveguide formed on the substrate; and a modulation electrode (not shown) for modulating a light wave propagating the optical waveguide. A light-receiving element 5 is arranged so as to cross an output waveguide 24 constituting the Mach-Zehnder type optical waveguide and is formed so as to receive two radiation beams emitted from the multiplexing part of the Mach-Zehnder type optical waveguide. In the light-receiving element, two or more light receiving parts (51 and 52) are separately formed on one light-receiving element substrate 55.