基于石英(SiO2)制作光弹调制器(PEM)的压电驱动器时, 存在机电耦合系数小、需高压驱动且谐振频率随温度漂移严重等缺陷,故本文研究了PEM的优化设计方法。考虑铌酸锂(LiNbO3)特殊的晶体结构, 从理论上推导了LiNbO3晶片作为压电驱动器的可行性, 并确定其切型为zyw/35°切。基于有限元分析软件COMSOL4.3a仿真, 确定了晶片体积和谐振频率, 设计了LiNbO3压电驱动器。对设计出的压电驱动器进行了压电性能测试, 并和SiO2压电驱动器进行了比较。将LiNbO3压电驱动器和硒化锌(ZnSe)光弹晶体组合成PEM, 用671 nm激光进行了光弹调制实验。实验结果表明: 实现相同位移时, SiO2压电驱动器需要的驱动电压是LiNbO3压电驱动器的100多倍, 且后者横向长度伸缩振动模式单一性和稳定性均优于前者。驱动电压为3.76 V时, 671 nm的激光通过基于LiNbO3压电驱动器的PEM的调制光程差为3.7 μm。得到的结果表明: 基于LiNbO3压电驱动器的PEM易于驱动控制, 调制性能优于基于SiO2 驱动器的PEM。

When the quartz(SiO2) is used as the piezoelectric actuator of a photoelastic modulator(PEM), it has shortcomings of smaller electromechanical coupling coefficient, high driving voltage required, and serious frequency drifting with a temperature. Therefore, this paper designs an optimized PEM. In consideration of the special crystal structure of lithium niobate (LiNbO3), the feasibility of LiNbO3 crystal to be a piezoelectric actuator was verified and its cut shape was set as zyw/35°cut. Based on the finite element analysis software COMSOL4.3a simulation, the chip size and the resonant frequency were determined. Then, a LiNbO3 piezoelectric actuator was designed. The piezoelectric performance of the piezoelectric actuator was tested and compared with SiO2 piezoelectric actuator. Finally the LiNbO3 piezoelectric actuator was combined with a ZnSe crystal to construct a PEM, and it was performed a photoelastic experiment by a 671 nm laser. The experiment for achieving the same displacement show that the drive voltage for the SiO2 based piezoelectric actuator is 100 times that of LiNbO3 based piezoelectric actuator, and the unity and stability of lateral length stretching vibration mode for the latter is better than that for the former. Moreover, when the drive voltage is 3.76 V, the optical path difference of 671 nm laser will be modulated to 3.7 μm through the LiNbO3 piezoelectric actuator based PEM. These results demonstrate that proposed LiNbO3 piezoelectric actuator based PEM is easy to drive and control and the modulation performance is better than that of previous PEMs.