CONTROLLING METHOD FOR COUPLING LENGTH OF OPTICAL DIRECTIONAL COUPLER

摘要

PURPOSE:To realize the monitor control for the degree of coupling, by loading a material thin film which varies its refractive index by the irradiation of light on a waveguide path at one side of an optical directional coupler. CONSTITUTION:An optical directional coupler is formed by two optical waveguide paths 2 and 3 which are put close and in parallel to each other on a substrate 1. A thin film 4 of chalcogenide amorphous semiconductor, etc. which varies its refractive index by the irradiation of the light of a short wavelength is loaded on the path 3 with a thickness less than the cutoff wavelength. While the laser is put into the path 2. Then the laser of an He-Cd laser 7 is irradiated to the film 4 from the end to the center part while monitoring the intensity of the laser radiated fron the path 3 by the directional coupling by a detector 5.