Study on signal 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, strict match size, bulky et al., we proposed a photo-elastic modulate mode which use LiNbO₃ crystal piezoelectric properties to produce the effect of the photo-elastic. According to the theory of piezoelectric vibration and Crystal optics principle, we analyzed the crystal orientation dependence of physical properties, and derived the relations of displacement and retardation amplitudes over voltage amplitude, then, the cut-type and the optical path was been optimized. The device was 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 offers basic modulation frequencies at 73.71kHz corresponding to the longitudinal oscillations in x- direction. Finally, the correlation experimental equipment was built for the experimental verification; the result shows that: the voltage amplitude to achieve a half-wave retardation amplitude is only ~1.6 V for 633nm wavelength, the modulation voltage reduced ~4 times Compared with the LiTaO3 signal crystal photo-elastic modulator whose cutting-type didn´t been optimized . The SCPEM will have larger dynamic modulation range and lower modulation power dissipation; in addition, the light damage threshold of this SCPEM will be high, and modulation frequency can be further improved till hundreds of kHz or several MHz. It has important application prospect in the field of super-laser pulse modulation, super-speed interference modulation and so on.