Development of Tunable Optical Filters for WDM Optical Communication Using High Coupling SH-Type Surface Acoustic Waves

这项研究计划的目的是开发高效率光学过滤器wavelength-division-multiplexing （WDM）光学通信by utilizing interaction between highcoupling SH (shear-horizontal)-type surface acoustic waves and optical TE- and TM-mode waves. The在这个项目中所支持的follows：1.这已经存在了BGS wave， which is a pure shear surface acoustic wave，on the metalized surface of Z-axis cylinder cuts of KNbO D23 D2，and the electromechanical coupling factor ki D12 D1 is very high，2. The change of refractive index induced by The BGS wave on Z-axis cylinder cuts ofD2 has been analyzed and the results revealed the index change to be 18 times larger thanthat of the conventional Rayleigh waves. 3. By depositing a ZnO film with a low shear wave velocityon the Y-X LiNbO - D23 - D2 substrate the leaky SH-type surface wave is turned into a non-leakySH-type surface wave with no propagation loss and the K - 12 - D1 is high as 21.4% for the ZnOfilm thickness about 0.1λ。This has been experimentally proved. 4. The refractive index changeinduced by the SH surface wave on ZnO/Y-X LiNbO - D23 - D2 has been shown theoretically to be largenear the substrate surface compared with那些Rayleigh waves. the coupling length needed for100% ted - tm mode conversion has been calculated using the coupled-mode theory to be关于1/2.5 ofthat of the Rayleigh wave. 5. ZnO/Y-X LiNbO D23 D2 acousto-optic tunable filters have been设计和结构. The experimental evaluation of tetm mode conversion characteristics are现在的投资者。

The purpose of this research project is to develop high efficiency tunable optical filters for wavelength-division-multiplexing (WDM) optical communication by utilizing interaction between high coupling SH (shear-horizontal)-type surface acoustic waves and optical TE- and TM-mode waves. The results obtained in this project are summarized as follows : 1. It has been shown that there exists the BGS wave, which is a pure shear surface acoustic wave, on the metalized surface of Z-axis cylinder cuts of KNbOィイD23ィエD2, and the electromechanical coupling factor KィイD12ィエD1 is very high, about 53%. 2. The change of refractive index induced by the BGS wave on Z-axis cylinder cuts of KNbOィイD23ィエD2 has been analyzed and the results revealed the index change to be 18 times larger than that of the conventional Rayleigh waves. 3. By depositing a ZnO film with a low shear wave velocity on the Y-X LiNbOィイD23ィエD2 substrate the leaky SH-type surface wave is turned into a non-leaky SH-type surface wave with no propagation loss and the KィイD12ィエD1 is as high as 21.4% for the ZnO film thickness about 0.1λ. This has been experimentally proved. 4. The refractive index change induced by the SH surface wave on ZnO/Y-X LiNbOィイD23ィエD2 has been shown theoretically to be large near the substrate surface compared with those of the Rayleigh waves. The coupling length needed for 100%TE-TM mode conversion has been calculated using the coupled-mode theory to be about 1/2.5 of that of the Rayleigh wave. 5. ZnO/Y-X LiNbOィイD23ィエD2 acousto-optic tunable filters have been designed and fabricated. The experimental evaluation of TE-TM mode conversion characteristics are now under investigation.