| 摘要 |
PURPOSE:To obtain a high extinction ratio by disposing plural pieces of flat plate electrodes in positions asymmetrical with an optical waveguide. CONSTITUTION:The flat plate electrodes 3A, 3B are disposed to face each other with the optical waveguide 2 disposed to a substrate 1 in-between. The optical waveguide 2 is disposed in proximity to one (3A) of the flat plate electrode. The refractive index of the crystal as the substrate 1 changes owing to an electrooptic effect, piezo-electric effect and photoelastic effect when an electric field is applied to the crystal. The light is not confined into the waveguide and is radiated into the substrate under the electrode in proximity to the optical waveguide. When the effective refractive index of the substrate under the electrode and the refractive index of the optical waveguide are made equal. The difference in the impressed electric fields between the waveguide 2 and the inside of the substrate 1 under the electrode is larger with the element in which the width of the electrode 3A in proximity to the waveguide 2 is narrower than the width of the other electrode 3B than in other cases and therefore the highest extinction ratio is obtd. |
