| 摘要 |
PURPOSE:To reduce the reflection loss on a connection surface with an optical fiber and to provide excellent temperature characteristics suitable to a waveguide type A/O element, etc., by providing a substrate made of single crystal of lithium tetraborate and an optical waveguide area which has a higher refractive index than that in the substrate or of its surface. CONSTITUTION:A Ti thin metallic film 2 (200-500Angstrom ) is formed on the LBO single-crystal substrate 1 and patterned corresponding to a specific optical waveguide by lithography; and the substrate 1 is heated at high temperatures and Ti atoms are diffused into the LBO substrate to form the optical waveguide. Even when the optical waveguide is connected to an optical fiber, the reflection factor is <=0.5X10<-3>, so the reflection loss on the connection surface is reduced to about 1/300 as compared with the use of, for example, LNO. Further, LBO has various optical properties that LNO has and is superior in temperature characteristics of, specially, a surface acoustic wave SAW and LBO posseses such an azimuth that the temperature coefficient of the propagation speed of the SAW approximates to 0 almost at room temperatures. |
