The Fabrication,Electro-Optical Properties And Application Studying Of Polymer Dispersed Liquid Crystal

Polymer dispersed liquid crystal(PDLC)is a kind of electro-optic material with excellent properties formed by liquid crystal droplets dispersed in polymer matrix.Compared with traditional nematic liquid crystal based devices,PDLC based devices have many excellent features,such as polarization independent,easy fabrication,no moving parts and low cost.Thus electrically switchable PDLC based devices have played important roles in the field of electro-optic devices.The electro-optical properties of PDLC have great influence on the performance of applications based on PDLC.In this paper,we fabricated the PDLC based variable optical attenuator(VOA),and study the electro-optical properties of the PDLC-VOA.Then the influences of the material ratio and the preparation process on the performance of PDLC-VOA are also studied.This work provides experimental and theoretical fundamental understanding for the design and fabrication of PDLC-VOAs with different performance.PDLC samples are fabricated by polymer induced phase separation(PIPS)method.Then the electro-optical properties of the PDLC sample are measured with an optical measurement system.With the increase of voltage,the transmittance of the PDLC sample increases.Changing the incident angle will significantly change the transmittance of the PDLC sample.The larger the incident angle,the lower the transmittance of the sample.The experimental results of the PDLC response time show that the target voltage affects the rise time of PDLC.The rise time decreases with the increase of the target voltage,while the decay time increase with the increase of the initial voltage.With the increase of the voltage,the hysteresis effect becomes severe.Based on these,we studied the effect of material ratio and UV intensities on the performance of electro-optic properties of PDLC.With the increase of polymer proportion in PDLC material,the size of liquid crystal droplets becomes smaller and formed PDLC becomes more uniform.Correspondingly,the contrast ratio,the rise time increase,threshold voltage and saturation voltage increase,while the decay time decreases.Hysteresis effect becomes more severe when the proportion of polymer increases.The PDLC-VOA has smaller minimum insertion loss and larger attenuation range with the increase of polymer ratio.With the increases of the UV intensity,the size of liquid crystal droplets decreases,the threshold voltage and saturation voltage increase.The rise time increases while the decay time decreases for high intensity UV irradiation.The hysteresis effect also becomes severe.The minimum insertion loss of PDLC-VOA decreases and the attenuation range increases as the UVintensity increases.The work suggests that it is possible to optimize the electro-optical of PDLC by adjusting the material ratio and preparation process and obtain PDLC-VOA with different electro-optical performance.