Patent ID: 8542963

Claim:
An optical transmission substrate that transmits an optical signal, the optical transmission substrate having a main surface and comprising: an optical waveguide; two clad layers for enclosing the optical waveguide there between; and an optical coupling unit provided in a trench that opens in the main surface of the substrate, substantially perpendicular to the optical waveguide and in close contact with an end face of the optical waveguide, a depth of the trench spanning from the main surface of the substrate and through an entirety of the depths of the optical waveguide and the two clad layers; wherein said optical coupling unit includes a three-dimensional polyhedral light-reflecting member formed of a monocrystal inorganic solid non-metal wafer and having a mirror surface that obliquely intersects the optical axis of the optical waveguide to provide the optical transmission substrate with a structure for optical coupling with the outside, wherein a width of the three-dimensional polyhedral light-reflecting member corresponds to a width of the trench, and a depth of the three dimensional polyhedral light-reflecting member corresponds to an entirety of the depth of the trench, and wherein the three-dimensional polyhedral light-reflecting member has a scalene triangular cross section, and a plurality of surfaces, other than the mirror surface, of the three-dimensional polyhedral light-reflecting member are in face-contact with the inner wall surfaces of the trench.