JPS5666818A - Magneto-optic thin film photo circuit element - Google Patents

Abstract

PURPOSE:To obtain a nonantimetrical photo circuit element which is small in size, is stable and permits easy integration by selecting the widths etc. of two sets of optical guides provided to a magneto-optic substrate having Faraday effect at predetermined values and making the propagation phase constant of both guides equal. CONSTITUTION:An optical guide 3 and a thick and convex optical guide 4 of a shape are provided in proximity on a garnet substrate 1 having Faraday effect. If the widths W1, W2 of these optical guides 3, 4 are changed and are so selected that the propagation phase constants of the guides 3, 4 for TE mode light and TM mode light become equal, the equivalent refractive indexes of the guides 3, 4 become equal. Hence, the TE mode light propagated in the guide 3 by the Faraday effect owing to a magnetic field 7 cozes into the guide 4, where it is converted to the TM mode light, whereby photocoupling is accomplished. The TM mode light going reverse in the guide 4 does not couple to the TE mode light and propagates straightly in the guide 4. With this constitution, the nonantimetrical magneto-optic thin film photo circuit element becomes small in size, stable and easy to integrate.