Study On Holographic Polymer Dispersed Liquid Crystal Gratings

Holographic Polymer Dispersed Liquid Crystal Gratings(H-PDLCs)have unique application advantages in holographic display,optical communication,optical switches,filters,multi-focus lenses,etc.due to their electrical control characteristics.In order to prepare transmissive H-PDLCs with excellent performance and stable structure,it is of great significance to study the preparation and working field strength of transmissive H-PDLCs.Firstly,theoretical analysis and simulation study of the electro-optical effect of liquid crystal were carried out on the preparation and electrical control performance of H-PDLCs.Based on the introduction of the formation of photopolymer grating and the electro-optic anisotropy of liquid crystal,the formation and working principle of H-PDLCs structure are analyzed.And through the simulation of the phase modulation characteristics of the large aperture ring electrode type LC lens,the deflection of the liquid crystal in the electric field is studied.The change in (?)n caused by the deflection of the liquid crystal due to the field strength is the main factor that affects the diffraction efficiency of the grating,and is also the reason for the change in the electronically controlled diffraction efficiency.The preparation study of H-PDLCs was also carried out:the holographic prepolymer materials,the preparation process of the liquid crystal cell,the diffraction efficiency of H-PDLCs and the electric field control performance were studied.In the absence of an external electric field,the first-order transmission diffraction efficiency of the prepared H-PDLCs is between 10%and 60%.There are three main factors affecting the change of diffraction efficiency,interference light energy,ultraviolet curing time and angle of interference light,where the interference light energy is determined by the incident light power and the exposure time.When the incident light power density is 13.13m W/cm~2,the exposure time is 140s,the ultraviolet curing is 10min,and the interference angle 2?is 10°,the diffraction efficiency is the largest,about 54%.At the same time,the angular selectivity of the prepared H-PDLCs was measured,and the half-width was only about 5.18°.The breakdown field strength of H-PDLCs with a liquid crystal cell thickness of 10um is 15V/um.Under the working condition of 50Hz,5V/um?13V/um field strength,the change rate of the diffraction efficiency of the prepared sample can reach about 38.9%.