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液晶磁控偏光特性的研究 总被引:2,自引:1,他引:1
利用偏光干涉理论,通过对BL-009型向列相液晶透射比的测试,分析了液晶透射比随磁场的变化情况,并对液晶的磁控双折射效应进行了研究.实验在室温20℃下用JG-3型连续可调磁场仪对液晶盒施加垂直于其表面的磁场,用CT5A型特斯拉计准确读出磁场强度数值,使液晶盒光轴方向与起偏镜和检偏镜偏振方向成45°,分别测出了起偏镜和检偏镜偏振方向平行和垂直时的透射光强度.通过数学函数拟合,得出了液晶的双折射率随磁场的变化规律,即:当磁场强度大于液晶的阈值磁场时,拟合函数能很好地描述液晶磁控双折射率的变化规律. 相似文献
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液晶材料是信息显示设备中的重要组成部分,其在外场作用下所表现的高双折射特性是其被用于显示的关键条件。利用强太赫兹波作为外场,激发液晶5CB材料的双折射效应。结合太赫兹时域光谱系统通过测量不同偏振的太赫兹波的透过率,研究了太赫兹场致液晶在太赫兹波段的双折射效应。分析了液晶的双折射效应与外场强的变化关系、频率响应特性等方面。研究结果表明在强场太赫兹波激发下,液晶的双折射现象随场强的增大而增大,双折射值与外部场强平方成正比,且液晶5CB对于太赫兹激发的双折射效应存在一定的阈值。 相似文献
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To meet the application need for agile precision beam steering, a novel liquid crystal prism device with a simple structure, convenient control, low cost and applicable performance is presented, and analysed theoretically and experimentally. The relationships between the optical path and the thickness of the liquid crystal cell under different voltages are investigated quantitatively by using a theoretical model. Analysis results show that the optical path profile of the liquid crystal prism has a quasi-linear slope and the standard deviation of the linear slope is less than 16 nm. The slope ratio can be changed by a voltage, which achieves the programmable beam steering and control. Practical liquid crystal prism devices are fabricated. Their deflection angles and wavefront profiles with different voltages are experimentally tested. The results are in good agreement with the simulated results. The results imply that the agile beam steering in a scope of 100 μrad with a micro-rad resolution is substantiated in the device. The two-dimensional beam steering is also achieved by cascading two liquid crystal prism devices. 相似文献
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The nonlinear refractive index, n2, and the birefringence, Δn, of a nematic liquid crystal mixture (denoted as 1294-1b) doped with a anthraquinone derivative (denoted as AQ) dye were measured as a function of an external ac applied voltage. The self-phased modulation effect was used to measure the nonlinear refractive index of homeotropical-aligned samples. The change of the dyed liquid crystal nonlinearity, which is the direct impact of the applied voltage on the dye molecules orientation, was not observed for the nonlinear response of the pure liquid crystal. Planar (homogeneous) aligned samples were used for birefringence measurements by taking into account the absorption coefficients of the dye. The birefringence decreased to a limiting value in the high voltage region for both pure and dye-doped samples, although in the presence of the absorbing dye the birefringence of the liquid crystal was not approximately changed.The polarized absorption spectra of the dye in nematic mixture were recorded in parallel-aligned liquid crystal cell and its dichroic ratio R and the order parameter Sd were obtained. The electro-optical effect of the guest-host system was also using polarized spectroscopic method. 相似文献
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A versatile phase-stepping speckle shearing interferometer is described that employed a calibrated liquid crystal as its phase modulator, operating at 514 nm. By implementation of an algorithm upon phase-stepped shearographic images it was possible to create a phase map, that provided quantitative data regarding the derivative of any out-of-plane surface displacement. The use of a liquid crystal phase modulator in an optical arrangement had advantages over alternative methods. However, it is normally limited by spatial non-uniformity of the cells birefringence. The birefringence for a nematic liquid crystal cell was determined in several cross-sectional locations, before the cell was successfully integrated into a Michelson speckle shearing interferometer. Such a scheme offers flexibility in the shearing angle, and a measurement system that may operate over an extended range of monitoring wavelengths. 相似文献
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Optical studies have been carried out on two fluorinated isothiocyanato nematic liquid crystal (LC) compounds 4′-butylcyclohexyl-3, 5-difluoro-4-isothiocyanatobiphenyl and 4′-pentylcyclohexyl-3, 5-difluoro-4-isothiocynatobiphenyl. Transition temperatures of the two samples were confirmed using a polarizing microscope. The two LC compounds were found to exhibit fairly high clearing temperatures. Measurements of refractive indices of the two compounds were done by using thin prism method with He-Ne laser beam of wavelength 630 nm. Birefringence of the two LC compounds was calculated from the measured refractive indices. Both the compounds are found to display fairly high values of birefringence. Validation of a modified four-parameter model, based on Vuks equation describing the temperature dependence of refractive indices of the two liquid crystals, is also presented in this paper. The model is validated by fitting the experimentally measured values of refractive indices, birefringence and average refractive indices of the two nematic LCs with the theoretical values. In this paper, the calculation of order parameters of the LCs is presented by using two methods: direct extrapolation method based solely on the birefringence data and by using modified Vuks method based on Haller’s extrapolation. As observed from the obtained results, this procedure of calculating order parameter gives very reasonable results. 相似文献
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K. Kowiorski J. Kędzierski Z. Raszewski O. Chojnowska K. Garbat 《Phase Transitions》2016,89(4):403-410
ABSTRACTWedge cells of small apex angle, filled with liquid crystals, were used to determining optical characteristics as functions of temperature for three liquid crystalline mixtures recently produced and a reference nematic. The interference fringes appearing in polarised monochromatic light (of sodium yellow line) normally incident on the cell were exploited to measure the ordinary and extraordinary refractive indices in the reflection mode and birefringence in the transmission mode. The measurements were repeated using Abbe's refractometer for 6CHBT as the reference to verifying the precision. Additionally the order parameter was computed from birefringence as a function of temperature. The results confirm the usefulness of the method and provide the properties of two nematic liquid crystals of small and large birefringence and one smectic liquid crystal of medium birefringence, recently produced. The experimental systems served also to investigating phase transition between the liquid crystals and the isotropic liquid at near-clearing temperature. 相似文献
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液晶波前校正器特性研究 总被引:1,自引:0,他引:1
利用808 nm大功率连续激光器研究了液晶的光功率承受特性结果表明,当功率密度为133 W/cm2时,液晶还能保持原有的光学调制特性,而且可以长时间稳定工作测定了液晶的波长色散特性,发现,随着波长的增加Δn值逐渐减少,近紫外300~400 nm波段Δn变化47%,而在400~780 nm变化量为28%,在780~900 nm Δn变化了2%还研究了温度对液晶波前校正器衍射效率的影响,随着温度的升高Δn逐渐减小,当温度从10℃升到90℃时,对于16台阶菲涅耳透镜,衍射效率下降了70%;但当温度在20℃变化10℃时,对4台阶菲涅耳透镜衍射效率最大变化量为1.7%,而对16台阶菲涅耳透镜,衍射效率降低了1.2%. 相似文献