声光可调谐滤波器中声波导的制作及性能测试

Fabrication and performance measurement of acoustical waveguide in acousto-optic tunable filter

以LiNbO3晶体为基底,SiO2/In2O3为镀膜材料,设计并制作了用于准共线型声光可调谐滤波器（AOTF）的声波导及其叉指换能器（IDT）,研究了制作工艺,实验测量了该声波导的传输性能。实验结果表明：在未加声吸收胶的声波导中,声表面波（SAW）来回反射,形成驻波,使能量叠加,影响了传输;而在加了声吸收胶的声波导中,SAW具有良好的传输特性,即射频频率在165-185MHz时,声波导传输的效率达到最高,符合AOTF滤波的中心频率范围。测试结果表明：该声波导能够满足声光滤波的要求,而且制作工艺简单、设计灵活,性能更高。

The design and fabrication of acoustical waveguide and interdigital transducer （IDT） in the quasi-collinear acousto-optic tunable filter （AOTF） was investigated experimentally by using SiO2/In2O3 film on LiNbO3 substrate. Its transmission performance was measured. The results show that the surface acoustic wave （SAW） in the acoustical waveguide without acoustical absorber was reflected back and forth, and then the standing wave was formed resulting in energy superposition, transmission performance was affected. However, the SAW with acoustical absorber achieved better transmission performance. The transmission efficiency of the acoustical waveguide reached the maximum when the RF frequency was tuned between 165 MHz and 185 MHz, which was in agreement with the filtering range of the AOTF. The measurement results imply that the acoustical waveguide satisfies the requirements for the acoustooptic filtering, and features the simple fabrication process, flexible design and better performance.