| Nowadays,liquid crystal materials can be seen everywhere.In addition to various liquid crystal panels in the display field,they are also very common as beam modulators in laser systems,such as liquid crystal wave plates,liquid crystal spatial light modulators,liquid crystal polarization devices and so on.However,in high power optical system,high laser energy injection will produce obvious thermal effect,which will cause additional beam modulation of liquid crystal optical devices,and even affect the use of them.This paper studies the influence of laser loading on the performance of liquid crystal optical devices,analyzes the evolution and failure mechanism of its regulatory performance under laser loading,and provides theoretical guidance for the preparation process optimization and practical application of liquid crystal optical devices.Specific research work is carried out as follow.(1)The basic structure,working principle and preparation process of liquid crystal optical devices were studied,and the platform for the preparation of liquid crystal optical devices such as liquid crystal wave plate was established.(2)A near-common optical path interference measurement system was designed and built.Based on the fringe movement method,the dynamic variation of maximum additional phase of liquid crystal wave plate under 1064 nm(Effective area:0.1 cm~2)continuous laser loading was studied.Combined with the actual temperature rise measurement technology,the mechanism of temperature on additional phase modulation of liquid crystal wave plate was analyzed.In 200 to 1500 m W laser loading,the additional phase of the liquid crystal wave plate increases with the increase of laser power,and finally tends to be stable.When the laser power is greater than 1700 m W,the liquid crystal wave plate has macroscopic morphology change.Based on the physical model of liquid crystal refractive index and temperature,the analysis shows that the additional phase of liquid crystal wave plate is caused by the temperature-induced change of liquid crystal refractive index.Based on the physical model of liquid crystal refractive index and temperature,it is found that the additional phase of liquid crystal wave plate is caused by the temperature-induced change of liquid crystal refractive index.In addition,the transmittance of liquid crystal wave plate under laser loading shows periodic change,which is related to the change of refractive index of liquid crystal multilayer structure.The temperature field model of liquid crystal wave plate laser loading is established,and the deposition process of laser energy in liquid crystal wave plate is analyzed.The simulation results show that under continuous laser loading,the laser energy absorbed by indium tin oxide(ITO)conductive layer is converted into heat and transmitted to polyimide(PI)layer and liquid crystal layer,and the temperature gradient in liquid crystal wave plate is very small.Although the overall temperature of the liquid crystal wave plate is low,the heat resistance of the liquid crystal layer is poor,and its performance is first affected or even failed.(3)When the additional phase of the signal wave surface is different,it needs to be analyzed in two dimensions.Based on two-dimensional fast Fourier transform,the ability of spatial resolution additional phase measurement is established.The phase extraction code of interference fringe is written.The least square method is used to unpack the wrapped phase,and the two-dimensional additional phase value is obtained when the phase is different. |
