Patent ID: 7680366

Claim:
An optical waveguide chip comprising: a substrate having a main surface; and an optical waveguide layer formed on the main surface of the substrate, the optical waveguide layer having a core portion that guides light and a cladding portion, the cladding portion including a central portion, at least a part of which is positioned between the substrate and the core portion, and a thin film portion that is positioned at a periphery of the central portion and that covers at least a part of a region of the main surface that includes an edge of the main surface, wherein the thin film portion is thinner than the central portion wherein the central portion has first side surfaces coinciding with the light entry/exit ends of the core portion and being apart from all edges of the main surface, and second side surfaces excluding the first side surfaces and being apart from all edges of the main surface, and wherein, at least a part of the thin film portion is positioned between one of the second side surfaces and the closest edge of the main surface with respect to the one of the second side surfaces, and a stepped portion is provided at an interface between the one of the second side surfaces and the Part of the thin film portion.