Research On Non-Mechanical Beam Steering Technology Based On Liquid Crystal Polarization Grating

Beam deflection technology is one of the most core technologies in space laser communication.The traditional mechanical beam deflection system has the problems of high power consumption,large volume,and complicated control mode,which cannot meet the requirements of low power consumption,high precision and high efficiency required by space laser communication systems,and is based on liquid crystal polarization grating.The liquid crystal beam deflection system meets the needs of the current stage.The liquid crystal polarization grating is such that the liquid crystal molecules are periodically arranged along the plane of the substrate,and the liquid crystal molecules can be directed to the rotating grating device by electronic control during the grating period.The deflection efficiency of the grating theory can reach 100%,the preparation process is relatively simple,and the molding rate is high.However,there are few researches on liquid crystal polarization gratings in China at present,and more efforts are needed to fill the technical gap in the field.This thesis explores the advantages of liquid crystal photo-alignment technology,and based on the principle of photo-alignment orientation,designs a liquid crystal light valve system comprising a TFT-TNLCD write unit and an azo dye SD1 orientation transfer readout unit to achieve liquid crystal High contrast intensity modulation of the light valve readout unit.A diffraction efficiency of ±1 order of 90.2% was prepared,and by controlling the cell thickness of the liquid crystal cell,the 0-order diffraction efficiency at a voltage of 0 was controlled to be about 5%.In this paper,the effect of applied voltage on diffraction efficiency is quantitatively studied.By this method,the three states of diffraction of the liquid crystal polarization grating can be theoretically controlled by modulating the polarization state of the incident light and the magnitude of the applied voltage.The polarization direction of the zero-order diffracted light is ascertained,and the polarization of the non-zero-order diffracted light is qualitatively studied.By studying the polarization characteristics of non-zero-order diffracted light,we also found that the use of applied voltage can not only control the intensity of diffracted light at all levels,but also control the polarization of polarized light at all levels,laying a foundation for further research on liquid crystal polarized gratings.