Patent ID: 7702195

Claim:
An optical waveguide, comprising: a main body having an optical waveguide path capable of propagating light having a predetermined wavelength along a first direction orthogonal to a second direction and a third direction that are orthogonal to each other, the light being polarized to the second direction, the optical waveguide path having an outlet allowing the light to escape, the outlet having a narrow portion of which the width relative to the second direction is smaller than the wavelength of the light; a definition face for defining the optical waveguide path, the definition face including a pair of opposite face portions opposed to each other in the second direction, each opposite face portion being formed of a plasmon active substance at least in a portion that corresponds to the narrow portion; and a projection formed in a substantially pyramidal or conical shape provided at the main body, the outlet opening in the projection so that at least part of the narrow portion is located at a distal end of the projection, the outlet having a pair of aperture edges being opposed to each other in the second direction, the aperture edges being displaced from each other by a distance that is smaller than the wavelength of the light with respect to the first direction in a portion corresponding to the distal end of the projection; wherein the projection includes a pair of protrusive pieces that are opposed to each other with the outlet in between, and wherein distal ends of the protrusive pieces are displaced from each other with respect to the first direction.