FORMATION OF OPTICAL WAVEGUIDE

PURPOSE:To form a diffusion layer of an optical waveguide to a dielectric substrate, by irradiating the optical energy to the surface of the transparent dielectric substrate after forming a metallic thin film for optical waveguide in order to produce a reaction between the metallic thin film and the dielectric substrate. CONSTITUTION:A metallic thin film 12 is formed on the surface of a dielectric substrate 11 and at the part where an optical waveguide is formed. Then the light energy is irradiated from a light source 14 through the rear side of the substrate 11. The light energy is not virtually absorbed by the substrate and absorbed by the film 12. Then the heat is selectively generated to produce a reaction between the film 12 and the substrate 11. As a result, a metal (e.g., titanium) is diffused into the substrate 11. The absorbing coefficient of the optical energy of