| 摘要 |
PROBLEM TO BE SOLVED: To provide a directional coupler with which a problem of the polarization-dependability of the directional coupler is solved, thus integrality and a scale expansion are excellently preceded. SOLUTION: In the directional coupler having a substrate and two optical waveguides arranged close to each other on the substrate, the section of the core part of the optical waveguide is rectangular, the length of the rectangular side which is parallel to the main plane of the substrate is shorter than the rest of the sides. |
