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

本研究项目的目标是开发高效率、可调谐的光学过滤器，用于波长度-分-多路复用（WDM）光学通信通过高耦合SH （shear-horizontal）-类型表面声学波和光学TE-和TM模式波之间的有效交互。该项目中获得的结果已被总结为以下： 1。它已经展示了BGS波存在，其中是一个纯剪切表面声学波，在KNbO的金属表面的Z-axis cylinder切割的KNbO的金属表面上D23的Y D2， and the electromechanical coupling factor Kyi D12的Y D1非常高，大约53%。2. The change of refractive index induced by the BGS wave on Z-axis cylinder cuts of KNbO-D23-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-D23-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-D12-D1 is as high as 21.4% for the ZnO film thickness about 0.1\。这已经被实验证明了。4. The refractive index change induced by the SH surface wave on ZnO/Y-X LiNbOイイD23イエD2 has been shown theoretically to be large near the substrate surface compared with those of the Rayleigh waves。100%TE-TM模式转换所需的配对长度已经使用该配对模式理论计算约为雷利波的1/2.5。5. ZnO/Y-X LiNbO-D23-D2 acousto-optic tunable filters have been designed and fabricated。TE-TM模式转换特性的实验评估现在正在进行调查。

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.