Patent ID: 6870979

Claim:
An optical circuit comprising: a silicon substrate; an optical waveguide layer formed on the silicon substrate, the optical waveguide layer having a core and a cladding; and temperature control row formed on the optical waveguide layer, for variably controlling the temperature of a portion of the core locally; wherein the optical waveguide layer on both sides sandwiching a portion on which the temperature control means is formed is removed from a region spaced from the core along a longitudinal direction of the core, from a surface of the optical waveguide layer to a surface of the silicon substrate; a recessed portion having a rectangular cross-sectional shape is provided in a surface portion of the silicon substrate including an entire region facing a bottom part of the optical waveguide layer-removed portion; the surface of the silicon substrate is formed of a silicon (100) crystal plane, a side face of the recessed portion formed along the longitudinal direction of the core is formed of a silicon (100) crystal plane substantially perpendicular to the silicon substrate surface, and a bottom face of the recessed portion is formed of a silicon (100) crystal plane substantially parallel to the silicon substrate surface.