| As a kind of key elements in the advanced optical information processing systems, spatial light modulator (SLM) can be used as a objective function for input, or it can be also used as a spatial filter on the frequency plane. Especially, phase-only SLM devices were applied to eletro-optical information systems extensively because of the merits of high light efficiency and high diffractive efficiency. With the development of liquid crystals displays technology, LC devices were used as EA-SLM comprehensively. Thin-film-transistor (TFT) liquid crystal devices were studied in many literature, because of design feature of TFT, there are some defects to apply TFT to optical information processing, such as its low aperture opening ratio (low light efficiency), low resolution etc. Recently, one novel LC device LCoS interested people's attention because it high aperture ratio and high resolution. LCoS device should be applied to optical information processing field more comprehensively.This dissertation describes the distribution of director of liquid crystal based on the theory of continuous elastic materials, and then several methods to describe the propagation of light wave in liquid crystals materials were introduced, the principle of phase modulation of light wave by liquid crystals was expounded.First we depicted one theoretical model of LCoS device, and then working modes of LCoS used as phase-only SLM were selected and optimized by varied the twist angle of liquid crystals and polarized angle due to parameter space method, two working modes, which are suitable to apply LCoS as phase-only SLM, were found, that is (0°, 0°) and (0°, 52°). Theoretical study also showed that the (0°,52°) could be used as a compound device, it behaved property of intensity modulation if a working point was selected appropriately and it behaved property of phase modulation when another wording point was selected. At the same time, this two working modes were studied detailed by extended Jones matrix method. Theoretical analysis showed that LCoS device which working on this two working modes can be used as phase-only SLM. For verify this result, the LCoS phase-only SLM was assembled working on (0,52°) mode, and also we design one experimental system to measure the phase modulated amount based on the interferometer. The properties of LCoS device weremeasured and the changing of reflectivity accorded with phase modulation of LCoS device was also checking. Experimental results showed that LCoS device can realized a 1.9π dynamic phase modulation with a reflectivity changing less than 5%. These results acknowledge that LCoS device can be used as phase-only SLM.One LC cell (Passive Matrix) was fabricated, which had six pixels and worked on (0°,0°) mode. Its phase properties were measured by compensator, because the high An liquid crystal material was used, the phase modulated amount of this LC cell can be larger than 4π while the reflectivity changing was less than 10%. Experiment verified that the phase modulation of LCoS device, which worked on (0°,52°) mode, could exceed 2π if the high birefringence LC material was adopted.Two applications of LCoS phase-only SLM were introduced, first programmable zoom Fresnel lens was realized based on LCoS. The focal properties of varifocal Fresnel lens was studied in experimental, experimental results showed that the deformation of surface of LCoS will lead to diffusion of the focal of Fresnel lens, one correction method was mentioned.Fractals Fresnel zone plate (FZP) was one novel element to applied to optical focusing. Based on our LCoS phase-only SLM, FZPs with variable lacunarity were fabricated, and the focalized properties of FZPs with variable lacunarity were studied in detail with n=4. The distribution of intensity on axis of FZPs was explored in theory and experiment, one formula was deduced to describe the distribution of intensity on axis of FZPs with n=4. Experimental results and values in theory were accordant well. Experimental results showed that the radius of focal spot would increase with the longer focal length, and focal depth would decrease with higher order of FZPs.
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