| 摘要 |
PROBLEM TO BE SOLVED: To make the phase error at the phase control part of the optical circuit element less than usual. SOLUTION: The phase control part 20 consists of a plane waveguide 11 and arcuate low-refractive-index areas 131 to 135 which are provided in the plane waveguide 11 and meet requirements (1) to (3). (1) The arcuate low- refractive-index areas are equal in curvature, but different in length. (2) The arcuate low-refractive-index areas have the convex sides of the arcs in the same direction and are arranged in parallel in the said direction in order from shorter one. (3) The arcuate low-refractive-index areas are so arranged that when segments corresponding to tangents at their end parts are extended out of the low-refraction areas, a point P on which the segments converge is generated. |
