| 摘要 |
PURPOSE:To allow the exact adjustment of the coupling rate of an optical directional coupler and the optical path length of optical waveguides by applying heat to regions including the core parts of clad layers to generate a heat history, thereby changing the refractive index of the regions. CONSTITUTION:The effective refractive indices of the optical waveguides 1, 2 which are embedded in the clad layers 7, 8 or clad layer 7 disposed on, for example, a silicon substrate 9 and have the effect of propagating light are changed by utilizing the heat history of this material. The entire part of the optical waveguide circuit is subjected to a heating treatment in electric furnaces 41 to 45. The desired points of the optical waveguide circuit are otherwise subjected to the local heating treatment by the heat resistant heaters provided at the desired points on the optical waveguide circuit or irradiation with an energy beam. The heat history refers to a phenomenon that the refractive index value of the material of the clad layers 7, 8 or core parts 1, 2 of the optical waveguides 1, 2 varies with cooling conditions after heating to a high temp. The coupling rate of the directional coupler to be constituted in proximity to two pieces of the optical waveguides 1, 4 after the production of the optical waveguides is exactly adjusted in this way. |
