The Frequency Modulation Characteristic Of Holographic Polymer Dispersed Liquid Crystal Doped With Nano Ag

In recent years, holographic polymer dispersed liquid crystal(H-PDLC), being a ne w kind of optoelectronic holographic material, has widely potential applications in acad emic and industrial fields such as optical communication, flat panel display, optical data storage, and integrated optics.Generally, H-PDLC material needs a relatively high external voltage to drive rotati on of liquid crystal, which will mainly limit its application and development. We experi mentally prepared H-PDLC volume grating doped with moderate concentration of nano-Ag and obtained better electro-optical properties compared with H-PDLC without nano-Ag. In order to study the effect of driving frequency on the performance of the H-PDL C doped with nano-Ag, we do some theoretical and experimental work in this thesis incl uding two parts as follows:1. Study of driving voltage: We established an equivalent circuit model for H-P DLC doped nano Ag gratings according to Maxwell-Wagner effect and calculated relax ation frequency for different concentrations of nano Ag. We experimentally measured th e change curves of driving voltage with frequency. The results show that with the increa se of external voltage frequency, the threshold driving voltage of H-PDLC doped with n ano-Ag generally present an upward trend after decreasing. It is experimentally shown t hat the lowest threshold driving voltage can be obtained when the driving frequency is l ocated just around the recipe’s dielectric relaxation frequency. It is possible to decrease the driving voltage of H-PDLC through selection of suitable driving frequency as well a s via doping with appropriate concentration of nano Ag. For the samples with different c oncentration of nano-Ag(0.05%,0.1%,0.2%), the lowest threshold voltages were 1.2 V/u m(drive frequency 5 KHz), 5.5 V/um(drive frequency 8 KHz), 3.1 V/um(drive freque ncy 10 KHz) respectively.2.Study of response time: We theoretically analyzed the relationship between re sponse time of H-PDLC doped with nano-Ag and the driving frequency by referencing previous study results like the response time of liquid crystal, polymer dispersed liquid crystal, and pure liquid crystal with nano-Ag. We experimentally obtained the relationsh ip between response time of H-PDLC doped with different concentration of nano-Ag(0%,0.05%,0.1%,0.2%) and the driving frequency. The experimental results show that the rise response time of H-PDLC doped with nano-Ag was hardly influenced by the driving frequency, while the fall response time show non-monotonic trend that conforms to th e theory.