JPS5452562A - Variable wavelength selection filter - Google Patents

Abstract

PURPOSE:To make wavelength selection variable and further provide switching action by making use of the electro-optical effect of corrugation and substrates. CONSTITUTION:4 is a Y-cut LiNbO3 ferrodielectric substrate, 5 is a Ti diffused layer optical guide made through vapor deposition, etc. of Ti thin film, 6 is corrugations made of holography or the like and 7 is a voltage-applying Al electrode mad through vapor deposition, etc. When the light signal mixed with lambda1, lambda2, etc. is propagated in the optical guide 5, the wavelength lambda1 is branched by the corrugations having a diffraction grating width suitable for the Bragg's reflection conditions of the wavelength lambda1. The effective refractive index of the optical guide 5 is changed by applying a certain voltage in the Z axis direction of the substrate to the Al electrode 7. This causes the Bragg's reflection conditions to change even in the corrugation of the same diffraction grating width, thus enabling the signal of the wavelength lambda2 propagating next in correspondence to the change portion of the effective refractive index to be branched. This effective refractive index is variable with the applied voltage, hence the selection of the wavelengths is made variable, thus switching action by On and OFF may be effected.