BURIED TYPE DOUBLE DIFFRACTION TYPE LIGHT WAVEGUIDE OR CONSTRUCTION THEREOF AND MAKING THEREOF

PURPOSE: To make it possible to obtain sufficient double refraction within glass by providing striped waveguides with layers for imparting mechanical stresses having the components perpendicular to these waveguides to glass layers having prescribed refractive indices. CONSTITUTION: The glass layer GS1 is formed in the region B (where directional couplers RK2, RK3 exist and a directional coupler RK1 does not exist) on a substrate Sub. This glass layer GS1 has the coefft. of thermal expansion different from the coefft. of thermal expansion of the sheath glass of the waveguides having the prescribed refractive indices and elastic optical coefft. different from the elastic optical coefft. of the glass. The glass layer GS2 consisting of the sheath glass is formed on the glass layer GS1. Further, a glass layer having the refractive index larger than the refractive index of the sheath glass is formed thereon. This glass layer has the coefft. of thermal expansion which is the same as far as possible as the coefft. of thermal expansion of the sheath glass and the same elastic optical coefft. as the elastic optical coefft. of the sheath glass. This glass layer is etched away and only the waveguides LW1, LW3, LW21, LW32 are made to remain as the stripes in relief from the circumferences on the glass layer GS2.