基于铌酸锂压电弹光双效应的单晶体弹光调制器

为了克服Kemp型弹光调制器调制效率低、加工工艺困难及体积大等缺点，提出了采用铌酸锂(LiNbO3)晶体压电弹光双效应的单晶体弹光调制器的设计思想；根据压电振动理论和晶体光学原理，分析了晶体各物理量随空间变换的特性，推导了调制电压相位差振幅之间的关系，并对晶体切型和通光方向进行了优化，所设计的晶体尺寸为41 mm×7.7 mm×17.1 mm（x×y×z），切割角为0°（x切），通光方向z轴（光轴），通过在x-z面施加与晶体谐振基频一致的周期性电压，产生沿x方向，频率为73.71 kHz的伸缩振动, 最后通过实验对所设计单晶体弹光调制器进行了验证；实验结果表明，对633 nm激光进行半波调制时，该弹光调制器所需调制电压为1.6 V；与基于钽酸锂(LiTaO3)且未进行切型优化的单晶体弹光调制器相比，调制电压下降了约4倍。

Single Crystal Photo-Elastic Modulator Based on Lithium Niobate Piezoelectric and Photo-Elastic Effect

In order to overcome the disadvantage of Kemp-type photo-elastic modulator such as low modulation efficiency, processing technology difficulty, bulky et al., a photo-elastic modulation mode is proposed. Which uses LiNbO3 crystal piezoelectric properties to produce single crystal photo-elastic modulator. According to the theory of piezoelectric vibration and crystal optics principle, the crystal orientation dependence of physical properties is analyzed, and the relations of displacement and retardation amplitudes over voltage are derived. Then, the cutting-type and the optical path are optimized. The device is designed with dimensions 41 mm×7.7 mm× 17.1 mm in x-, y- and z-direction, 0° cutting angle (x-cut), z-axis for the optical path and electrodes on the xz-surfaces offer basic modulation frequencies at 73.71 kHz corresponding to the longitudinal oscillations in x-direction. Finally, the corresponding experimental equipment is built for the experimental verification; the result shows that: the voltage amplitude to achieve a half-wave retardation amplitude is only about 1.6 V for 633 nm wavelength, and the modulation voltage reduces about 4 times, compared with the LiTaO3 signal-crystal photo-elastic modulator whose cutting-type isn′t optimized.