| 摘要 |
PURPOSE:To obtain the optical directional coupler which has a different branch ratio at low cost by forming a clad layer between thin film layers which have coupling parts for one waveguide and tapered parts and controlling the branch ratio with the film thickness and/or refractive index of the clad part. CONSTITUTION:The clad layer 4 is interposed between the thin film layers 3 and 5 which has the coupling parts for one waveguide and the tapered parts and the branch ratio is controlled with the film thickness and/or refractive index of the clad layer 4. For example, the thin film layer 3 which includes the coupling part for a 1st waveguide 1 and the tapered part, the clad layer 4, and the thin film layer 5 which includes the coupling part for a 2nd waveguide 2 and the tapered part are formed in order on a substrate 6 to manufacture the 2X2 optical directional coupler. In this case, the film thickness of the clad layer 4 is controlled with the viscosity of liquid and the rotating speed of a coating device. Consequently, waveguides type optical directional couplers with various branch ratios can accurately be obtained at low cost. |
