Abstract: An object of the invention is to provide an optical integrated circuit substrate capable of establishing optical connection between an optical waveguide and a semiconductor light-receiving element with high light-receiving efficiency and of achieving low-loss light transmission. In the optical integrated circuit substrate, on a substrate is formed an optical waveguide having a clad and a core layer. Embedded in the optical waveguide are a metal placement portion for an optical element and a thin-film optical element placed thereon. Distance between the thin-film optical element and the core layer is reduced. In a region free of the thin-film optical element, there is an adequate distance between the core layer and the substrate. This allows satisfactory optical connection between the thin-film optical element and the optical waveguide. In the thin-film optical element-free region, low-loss light transmission is achieved without interaction between transmitted light and the substrate.

Abstract: An object of the invention is to provide an optical integrated circuit substrate capable of establishing optical connection between an optical waveguide and a semiconductor light-receiving element with high light-receiving efficiency and of achieving low-loss light transmission. In the optical integrated circuit substrate, on a substrate is formed an optical waveguide having a clad and a core layer. Embedded in the optical waveguide are a metal placement portion for an optical element and a thin-film optical element placed thereon. Distance between the thin-film optical element and the core layer is reduced. In a region free of the thin-film optical element, there is an adequate distance between the core layer and the substrate. This allows satisfactory optical connection between the thin-film optical element and the optical waveguide. In the thin-film optical element-free region, low-loss light transmission is achieved without interaction between transmitted light and the substrate.