| 摘要 |
PURPOSE:To improve the temperature stability by covering the top and reverse surfaces of optical waveguides in a substrate with a conductive film and connecting the whole conductive film electrically. CONSTITUTION:The optical waveguides are formed in the substrate 1 made of a ferroelectric material and the conductive film 6 is adhered uniformly to the entire surface including the top and reverse surfaces of the substrate 1 and connected electrically. The conductive film 6 is equal in potential at any place, so surface charges due to pyroelectric effect are short-circuited to prevent an electric field from being produced in the optical waveguides. Therefore, the directional coupler is formed of a material which has pyroelectric effect, the generation of charges due to temperature variation can be suppressed. |
