THIN FILM TYPE OPTICAL ELEMENT AND ITS MANUFACTURE

摘要

PURPOSE:To improve coupling efficiency and the efficiency of optical polarization or modulation by making the density distribution of the ion in an optical coupling part in the thickness direction of a substrate higher than on the inside than the front of the substrate and making the diffusion depth in the optical coupling part larger than in an optical function part. CONSTITUTION:A thin Ti film is deposited by evaporation on a substrate 1 after polishing and a thermally diffused Ti layer 21 is formed. A thin Cr film 22 is deposited by evaporation to an electrode forming part to form a mask and the substrate is subjected to anion exchange treatment to form a proton exchange layer 23 in the part not covered by the mask. The substrate subjected to such protion exchange treatment is subjected to a proton exchange treatment to form a proton exchange layer 24. The substrate subjected to twice the proton exchange treatment is subjected to an annealing treatment to form the optical waveguide layer 25 formed with the electrode parts as the diffused Ti layer 21 not implanted with the proton and the other part diffused with the proton into the substrate. The surface of the waveguide 25 except the region where a surface acoustic wave and guided light act with each other is subjected to a laser annealing treatment to form a low refractive index layer 26. Comb-shaped electrodes 28 are finally formed.