| 摘要 |
PURPOSE:To provide the optical waveguide element which lessens the coupling loss to optical fibers and propagation loss and decreases optical damages. CONSTITUTION:Crystal axes are so selected that the refractive index of a thin sheet 2 consisting of lithium niobate is larger than the refractive index of a substrate 1 consisting of lithium niobate having optical characteristics as a pure single crystal which is not subjected to an ion diffusion treatment to propagation mode of light. Two sheets of such substrates are directly joined, by which the incident light on the thin sheet 2 is confined in the thin sheet 2. Further, thin sheet 2 is provided with ridge structures, by which the parts of the lower parts of the ridges are made larger in actual dielectric constant than in the other parts and, therefore, the light is concentrically confined in the lower parts of the ridges. The lower parts of the ridges are consequently formed as guided light propagating parts 8 which act as optical waveguides 4, 5. The center of the guided light is the center of the optical waveguides 4, 5 or the point slightly intruding into the substrate 1 side and the shape thereof is circular. |
