| 摘要 |
PROBLEM TO BE SOLVED: To adjust the branch ratio of the optical waveguide type directional coupler to a specific value by providing a trench right above a coupling part where two optical waveguides are close to each other and charging a filler in the trench. SOLUTION: The optical waveguide type directional coupler having two optical waveguides put closely on a silicon substrate 1 has the trench 6 which is deep enough to reach a core 3 or shallower than that right above the coupling part 5 where the two optical waveguides are close to each other, and a 1st filler 7 is charged in the trench. The coupling state of the directional coupler is changed by varying the refractive index of the filler 7 charged in the trench 6, and the branch ratio can be changed. The branch ratio of the directional coupler is determined by the waveguide interval, the distance by which they are parallel (coupling length), etc. The waveguide interval of severalμm can not be made constant at the time of the manufacture. This operation is therefore utilized to adjust deviation of the branch ratio, caused owing to variance in the waveguide interval, from its design value. |
