| Liquid crystals with the ability to flow like liquids but also display symmetries inherited from crystalline solids are widely used in the areas of displays, phase modulator, information storage, optics switch and optical communication, and also have greatly promotion to the development of adaptive optics and integrated optics. However, the response time of traditional nematic liquid crystal electro-optic devices is really slow, usually in milliseconds range, or even several seconds. Blue phases exist between chiral nematic and isotropic phases with submillisecond response time, which makes it a promising candidate for next generation displays, tunable liquid crystal lens, phase gratings and phase modulators. Thus, fast response liquid crystal electro-optic devices are investigated in this thesis. New liquid crystal materials with fast response time are utilized, the electro-optic characteristics are studied, to overcome the shortages of high operation voltage and low efficiency of polymer stabilized blue phase liquid crystals (PS-BPLCs), new protocols to realize low operation voltage, fast response time and high efficiency blue phase liquid crystal electro-optic devices are designed and fabricated. The contents and results of this thesis are organized as follows:1. Fabrication of PS-BPLCs and the study of electro-optic properties of PS-BPLCs. Generally, PS-BPLCs contain three main components:nematic liquid crystal host to switch under the effect of electric field, chiral dopants to form double twist cylinder structure and two kinds of monomers to form polymer network. Ultraviolet (UV) exposure is always used to create uniform polymer network, which in turns helps broaden temperature range. We successfully fabricate PS-BPLCs and the stable temperature range is extended to -20～62℃ including the room temperature. Then, the content of chiral dopant is changed to adjust the Bragg reflection peak. The effect of different liquid crystal host and monomers to electro-optic properties are also studied. Based on this, we measure the dynamic response of PS-BPLCs to analyze the underlying physical mechanisms of hysteresis and submillisecond response time.2. Research on high resolution blue phase liquid crystal spatial light modulator (BPLC-SLM). High resolution and fast response time is the constant goal of the liquid crystal electro-optic devices. The fringing electric field effect caused by the voltage difference between two adjacent electrodes and the slow response time are two governing factors that determines the performance of high resolution LC-SLM. Firstly, the fringing electric field effect in a high resolution nematic LC-SLM is systematic studied by numerical modeling. Then, we present a reflective polymer-stabilized blue phase liquid crystal on silicon (PSBP-LCoS) device. The fringing electric field effect on the performance of the device is investigated. The PSBPLC phase modulator is polarization dependent under the effect of fringing electric field. General design issues related to the PSBP-LCoS configuration and phase profile properties are discussed, the operation voltage can be greatly decreased by using a large Kerr constant and large △ns BPLC material with the optimized cell gap. This work provides fundamental understanding for the feasibility of low operation voltage and high spatial resolution BPLC-SLM. Furthermore, to overcome the high operating voltage of a BPLC-SLM, a facile PS-BPLC phase modulator to achieve particularly low voltage and high resolution is proposed. By employing a specific external compact optical system setup, the driving voltage is reduced to 26.09V to obtain 2π phase change. The wavefront distortion caused by the fringing electric field can be automatically compensated to generate accurate phase profile for fast response liquid crystal phase modulator. This work provides a new protocol to realize liquid crystal on silicon based fast response and high resolution phase modulator. These work have been published in Optics Express and Applied Optics.3. High efficiency and submillisecond response blue phase liquid crystal tunable phase grating. A polarization independent switchable phase grating based on PS-BPLC is proposed. A high efficiency of 38% of the phase grating has been achieved because of the sharp rectangular phase profile which shows good agreement with the simulation results. The response time is in the submillisecond range, and the phase grating is independent of the polarization of the incident light. This work has been published in Journal of Applied Physics.4. Dual-period tunable phase grating using PS-BPLC. Dual-period tunable phase grating using PS-BPLC is demonstrated by controlling its driving scheme. The grating period, as well as diffraction angle, can be alternatively tuned through controlling driving scheme. For each period phase grating, the diffraction efficiency can be adjusted by changing the applied voltage and the experimental results agree well with the simulations. High efficiencies of 35.3% for the small-period phase grating and 28.7% for the large-period phase grating have been achieved because of the rectangular-like phase profile. Besides the property of being polarization independent, the proposed grating also possessed fast response time. Five switching ports can be obtained by alternatively changing driving schemes which makes it a promising optical element for diffractive optics. This work has been published in Optics Letters.
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