物理学报Issue(1)：014304-1-014304-7,7.DOI:10.7498/aps.65.014304
基于绝缘体上硅的一种改进的Mach-Zehnder声光调制器∗
An improved Mach-Zehnder acousto-optic mo dulator on a silicon-on-insulator platform
摘要
Abstract
The interdigital transducer (IDT) of the traditional Mach-Zehnder (MZ) acousto-optic modulator on a silicon-on-insulator (SOI) platform is located outside its two arms. The crest and trough of the surface acoustic wave (SAW) are used to modulate the two arms of the MZ interferometer so as to achieve a high modulation efficiency. Therefore, the distance between the two arms must be odd multiples of half acoustic wavelength. However, since the substrate is usually not uniform, the wavelength of the SAW changes as it transmits through the surface of the device. As a result, the exact distance between the two arms is difficult to choose. On the other hand, the SAW losses a portion of energy after passing through the first arm of the MZ interferometer, so the modulation of the second arm becomes much weaker. To solve these problems, we propose a new structure where its IDT is situated in the middle of the two arms of the MZ interferometer. With this scheme, the two arms of the MZ interferometer are located exactly at the crest and the trough of the SAW, while they are modulated with equal strength. In this paper, we first use the finite element method to simulate the acoustic frequency and the surface displacement of the excited SAW. Then we deduce the refractive index variations of all layers according to their acousto-optic effects. After that, we analyze the influences of different factors on the acousto-optic modulation efficiency, including the type and size of waveguide, the thickness of zinc oxide (ZnO) layer, and the area it covers, the number of electrodes, etc. These parameters are accordingly optimized to enhance the modulation efficiency. Modeling result based on COMSOL Multiphysics indicates that when the width of the strip waveguide is 6 µm, the ZnO layer covers only the area under the IDT and has a thickness of 2.2 µm, and the number of the electrodes is 50, the effective refractive index variation of the waveguide reaches 4.08 × 10−4 provided that the amplitude of the driving voltage is 1 V. This value is 12%higher than that of the traditional structure.关键词
声光调制器/绝缘体上硅/声表面波/COMSOL MultiphysicsKey words
acousto-optic modulator/silicon-on-insulator/surface acoustic wave/COMSOL Multiphysics引用本文复制引用
秦晨,余辉,叶乔波,卫欢,江晓清..基于绝缘体上硅的一种改进的Mach-Zehnder声光调制器∗[J].物理学报,2016,(1):014304-1-014304-7,7.基金项目
国家重点基础研究发展计划(批准号:2013CB632105)、国家自然科学基金(批准号:61177055,61307074)、浙江省杰出青年科学基金(批准号：LR15F050002)和中央高校基本科研业务费专项资金资助的课题.* Project supported by the National Basic Research Program of China (Grant No.2013CB632105), the National Natural Science Foundation of China (Grant Nos.61177055,61307074), the Science Fund for Distinguished Young Scholars of Zhejiang, China (Grant No. LR15F050002), and the Fundamental Research Funds for the Central Universities, China （批准号:2013CB632105）
