Patent ID: 7308180

Claim:
An optical waveguide comprising: a waveguide core having a cavity surrounded by the waveguide core; and a clad which encloses the periphery of the waveguide core and has a smaller refractive index than the waveguide core has, wherein the optical waveguide changes a direction of a part or all of propagated light by using a part or all of an interface between the waveguide core and the cavity as a reflecting surface; wherein an area, in which a projected area that is obtained by projecting the reflecting surface in the direction of the waveguide core overlaps with a cross-sectional plane of the waveguide core, is smaller than a cross-sectional area of the waveguide core; and a branched waveguide is formed therein which divides the propagated light incident to the waveguide core into light which reflects on the reflecting surface and light, other than light reflected at the reflection surface, which travels in linear propagation in the waveguide core.