| 摘要 |
PURPOSE:To reduce radiation loss and to increase a branch angle by providing both side parts in a branch part with a high-refractive-index part having a boundary surface which crosses the branch part slantingly so as to shift to the center of the branch part from a trunk optical waveguide to branch optical waveguides. CONSTITUTION:The three-dimensional trunk optical waveguide 1 and three- dimensional optical waveguides 2 and 3 which are branched from a terminal of the waveguide 1 in a Y shape are formed on a substrate. One high-refractive- index part 4 is provided on each side of the branch part. The high-refractive- index parts 4 increase in width from the optical waveguide 1 to the optical waveguides 2 and 3 and boundary surfaces between the high-refractive-index parts 4 and other parts of the optical waveguides 1, 2, and 3 are linear and cross the optical waveguide 1 and branch parts slantingly to the center part so as to shift to the center of the branch parts from the optical waveguide 1 to the optical waveguides 2 and 3. Those high-refractive-index parts 4 are provided, so the overlap of boundary distributions at the branch parts increases. Therefore, the radiation loss of the branch parts can be educed, so the branch angle can be increased. |
