Study On Phase Modulator With High-Speed Response

The phase type of liquid crystal spatial light modulator can modulate the amplitude of the incident wave by changing the phase. It has higher energy efficiency and higher diffraction efficiency when it was compared with conventional liquid crystal display mode, so it is widely used in the field of adaptive optics and information optics. However, the defect of low response speed of phase liquid crystal spatial light modulator has always existed.In order to realize the high-speed response of liquid crystal phase modulator, polymer network liquid crystal (PNLC) was used to manufacture the phase modulator whose response time is in the order of milliseconds and the principle of its lower response time has been analyzed. The detail work includes the following points:(1) Research the key parameters that influence the response time of polymer network liquid crystal. Samples were prepared by varying the polymerization temperature, UV curing intensity and polymerization time. The polymerization conditions effect on the morphology of polymer network and the dynamic response of phase change was studied, it has lower response time than other polymerization conditions when the polymerization temperature is 283K, the UV curing intensity is 130 mw/cm2 and the polymerization time is 20min.(2) Research the characteristics of light scattering and photo-electric of polymer network liquid crystal. The light transmittance of phase modulator made by polymer network liquid crystal has been measured using photoelectric detector. The light scattering property and the electro-optical property of polymer network liquid crystal have been studied. The optical pathway to measure the properties of phase modulator prepared by polymer network liquid crystal was provided. The V-T curve and the response time of polymer network liquid crystal were measured.(3) Research the morphology of polymer network in polymer network liquid crystal. The morphology of polymer network was mainly characterized by cross linked single fibrils, cross linked fibril bundles or even both, this conclusion is testified by SEM. The polymer network liquid crystal has fast response speed when the morphology is linked single fibrils.(4) Research the phase modulation of phase modulator prepared by polymer network liquid crystal. The phase modulator made by polymer network liquid crystal with single pixel was divided into two parts, named A and B. The part B was applied a certain driving voltage on it, while the part A without voltage on it. The digital holography microscopy has been used to measuring the phase modulation quantity of phase modulator prepared by polymer network liquid crystal. According the method, we build the optical platform for testing the phase distribution diagram of these two parts. The difference value of them is the precise phase modulation when the phase modulator is under driving voltage.Through investigate the influence of polymerization conditions, parameters of liquid crystal and frequency of the driving voltage to the response time of polymer network liquid crystal, the relaxation time has been controlled under 300?s and the rise time has been controlled under 200?s when the phase modulation is ?. The response time has been reduced by a large margin. The digital holography microscopy has been provided to measure the phase modulation. The experiment proves that polymer network liquid crystal can be used to realize the high-speed response phase modulator whose phase modulation is more than 2n.