Patent ID: 7158695

Claim:
An optical delay circuit comprising: first and second defect waveguides having respective portions substantially parallel to each other and separated by a first distance, each of the first and second defect waveguides including a line-shaped defect in a periodic refractive-index distribution structure of a single photonic crystal, wherein the first and second defect waveguides include a multiplexing/demultiplexing portion in which first portions of the first and second defect waveguides are closer to each other than the first distance, for multiplexing and demultiplexing light propagating through at least one of the first and second defect waveguides, and an optical delay portion extending from the multiplexing/demultiplexing portion and in which the first and second defect waveguides are substantially parallel to each other and separated from each other by the first distance so that light propagating in either of the first and second defect waveguides does not interfere with the light propagating in the other of the first and second defect waveguides.