Patent ID: 8098547

Claim:
An optical waveguide that is structured with a core that is a waveguide where light is propagated, a clad that surrounds the periphery thereof, and a spot size converter member; wherein a refractive index of a material composing the core is larger than another refractive index of a material composing the clad, wherein the core provides a light incidence plane end surface that is one side where light enters and a light emitting plane end surface where light propagated in the waveguide is emitted, and the light incidence plane end surface at which the light enters, a taper portion that is a plate-like body of a nearly trapezoidal shape when viewed from a level plane and where a rectangular cross-section gradually decreases when advancing internally from the light incidence plane end surface, a waveguide core part that is linked to a minimum cross-section part of the taper portion and that extends to a targeted waveguide position while maintaining the cross-sectional area of the minimum cross section part for mainly propagating the light in a single mode; and the taper portion that is the plate-like body of nearly a trapezoidal shape provides a first plane and a second plane of nearly a trapezoidal shape, and on both of these planes, a first triangular plate-like spot size converter member and a second triangular plate-like spot size converter member composed of the same material as the core material are respectively arranged and formed in a substantially symmetrical structure.