Diffraction Efficiency And Control Method Of Liquid Crystal Phased Array Device

Liquid crystal optical phased array devices mainly composed of liquid crystal spatial light modulator and cascaded liquid crystal polarization grating can realize beam deflection and shaping,and can be applied to space laser communication,laser radar,high energy laser weapons,etc.Compared with mechanical devices,it can reduce the volume and weight of the system and reduce power consumption.Liquid crystal spatial light modulator is a programmable device which modulates the spatial distribution of light wave phase and can deflect light beam with high precision and small angle range.Cascaded liquid crystal polarization grating is based on liquid crystal polarization grating and liquid crystal adjustable half wave plate,by controlling the phase to change the polarization state,the beam deflection can be further realized,and the beam deflection can be realized in low resolution and large angle range.At present,the static diffraction efficiency theory of liquid crystal spatial light modulator has been well known,but the instantaneous attenuation theory of diffraction efficiency in the process of achieving beam modulation of liquid crystal spatial light modulator has not been reported.Many scholars have studied the diffraction efficiency theory of monolithic liquid crystal polarization gratings,but the diffraction efficiency after the use of orthogonal cascade is unknown,and the control method to improve the diffraction efficiency has not been reported.In this paper,the instantaneous attenuation of diffraction efficiency in the process of beam deflection by liquid crystal spatial light modulator is studied,and the existence of instantaneous attenuation is verified by experiments.The Angle between incident liquid crystal tunable phase retarder and liquid crystal polarization grating was reduced by optimizing the control coefficient,and the diffraction efficiency of liquid crystal polarization grating was improved by optimizing the control voltage of liquid crystal tunable phase retarder.The feasibility of the proposed method is verified by experimental tests,analysis of experimental data and comparison diagram of diffraction efficiency before and after optimization control.