| 摘要 |
PURPOSE:To obtain a waveguide for an optical switch which has excellent characteristics while uniforming its refractivity distribution, by forming a prescribed waveguide pattern on a substrate and then etching the substrate except at the pattern, and forming the waveguide pattern into a ridge type by thermal diffusion. CONSTITUTION:On the substrate 10 of LiNbO3, etc., Ti is varpordeposited to form the waveguide pattern 11. Then, the substrate 10 is etched away by plasma (as shown by an arrow) except at the part under the pattern 11 nearly to thickness for the thermal diffusion of Ti. Then, a thermal diffusing treatment is carried out to form the waveguide 12. Thus, the diffusion of Ti stops longitudinally and is never performed in the lateral directions of the substrate 10, so when a voltage E is applied to an electrode 17 provided at the intersection part of the waveguide 13 for the optical switch, a wall 18 with low refractive index is formed, so that incident light A is diffracted in a direction C after total reflection. Incident light B, on the other hand, is refracted in a direction D. This refractive index distribution is made uniform and crosstalk characteristics and a light elimination ratio are superior to those of a conventional plane type waveguide, thereby reducing electric power applied to the electrode 17. |
