| 摘要 |
PURPOSE:To prevent a light beam from diverging from a waveguide, by diffusing a substance for lowering a refractive index of a substrate, along the outside periphery of a curved part of the waveguide having the curved part, so as to be roughly in parallel to said outside periphery. CONSTITUTION:The first Ti metallic pattern 4 is formed on an LiNbO3 substrate 3 and a thermal diffusion is executed, an optical waveguide 5 is formed, and a first diffusion area is formed. Subsequently, an MgO pattern 7 is formed on the outside periphery of a curved part of this waveguide 5 and a thermal diffusion is executed, and a second diffusion area 8 is formed. As a result, on the substrate of the curved part of the waveguide, a refractive index gradient for lowering a refractive index of the outside periphery side is formed, and a difference of the optical path length of the inside periphery part and the outside periphery part of the waveguide is compensated, therefore, divergence of a light beam in the curved part can be prevented. Accordingly, a radius of curvature of the curved part can be made much smaller, and the degree of integration of an optical circuit element can be improved. |
