聚合物网络稳定液晶膜的制备与研究

实验发现在液晶中添加少量的预聚物单体,利用光聚合诱导相分离的方法可以形成反型显示模式的聚合物网络稳定液晶膜。该膜在平时呈现透明态,在电场的调节下呈散射态。本文观察了在不同光照时间、不同光强下制得样品的聚合物网络织构,分析了在聚合过程中形成网络的形状、大小与致密程度,并对实验结果进行了相关的讨论。     

Preparation and characterization of vinyltriethoxysilane based inorganic–organic gel glasses dispersed 4′-n-pentyl-4-cyanobiphenyl nematic liquid crystal

Vinyltriethoxysilane based inorganic–organic glasses dispersed with 4′-n-pentyl-4-cyanobiphenyl nematic liquid crystal are designed to fabricate a new type of gel glass dispersed with liquid crystal. Scanning electron microscopy shows that the nematic liquid crystal phase, occupying the interconnected cavities, is continuously embedded in the inorganic–organic matrixes. The effect of the nematic liquid crystal weight concentration on the morphology is investigated. The differential scanning calorimetry shows that the nematic-isotropic transition temperature depends on the nematic liquid crystal weight concentration. The Raman spectra show that there are no obvious Raman frequency shifts, compared with pure nematic liquid crystal. The in situ diffuse reflectance FTIR spectra show that the integral intensity of bands of hydroxyls has not varied.     

向列相液晶中光学相位共轭技术的研究进展

对向列相液晶中光学相位共轭技术的研究进展进行了介绍,分析总结了向列相液晶中光学相位共轭过程的机理与实验方法,并对向列相液晶中的光学相位共轭技术的应用前景进行了展望。     

Phase separated composite films of liquid crystals

Phase separation of liquid crystals from a solution with polymers has long been studied and used to prepare polymer stabilized and polymer dispersed structures. They are formed by spatially isotropic phase separation. A new mode, in which the phase separation proceeds anisotropically, has recently been discovered. Known as phase separated composite films (PSCOF), the resultant structures are made of adjacent parallel layers of liquid crystal and solidified polymer. PSCOFs have been made with nematic, ferroelectric (FLC), and antiferroelectric (AFLC) liquid crystals. Liquid crystals in PSCOFs exhibit electro-optical properties not observed in devices prepared by conventional methods, polymer dispersion, or polymer stabilization methods. Devices incorporating FLCs possess grey scale and switch 100 times faster at low fields than conventional surface stabilized devices. This method makes it possible to prepare very flexible devices and devices with liquid crystal film thickness comparable to optical wavelengths with great ease.     

铁电液晶螺旋结构的理论近似研究

由铁电液晶（FLC）手性近晶C相下螺旋结构的理论近似计算得出FLC一个螺距内平均折射率的表达式,根据表达式可得出一个螺距内的FLC分子作为一个整体可以看成一个向列相液晶分子模型的结论.当FLC沿螺旋轴方向的厚度等于FLC螺距的整数倍时,液晶盒内垂直取向的FLC分子可看作向列相液晶模型组成的集合.ZLI-3654型FLC与5CB型向列相液晶的实验结果验证了上述结论,理论结果和实验结果一致.这一理论可为畸变螺旋FLC和垂直排列畸变螺旋FLC器件的制备以及FLC的应用提供理论指导和更深的认识. 关键词： 铁电液晶 螺距 平均折射率 向列相液晶     

掺杂对液晶磁场弗里德里克斯转变影响的探讨

采用相位延迟法，通过对分别掺入微量卟啉类物质、纤维蛋白质和双偶氮苯沿面排列5CB液晶磁场弗里德里克斯转变的实验和数值计算，从实验和原理上探讨了微量掺杂对沿面排列5CB液晶磁场弗里德里克斯转变的影响.数值计算结果与实验相符，呈现两种转变过程.研究表明，掺杂物的磁学性质不同、分子的形状和大小不同对液晶弗里德里克斯转变和弗里德里克斯转变阈值的影响不同.进一步的掺杂2-benzothiazolethiol-linked porphyrinatozinc(Ⅱ)实验说明了这种情况. 关键词： 液晶 掺杂 弗里德里克斯转变     

Synthesis and reconstruction of computer generated holograms by a double pass technique on a twisted nematic-based liquid crystal spatial light modulator

Achieving phase only modulation from a spatial light modulator (SLM) is useful for many optical processing tasks. In this paper, we demonstrate a simple method of decoupling phase and amplitude modulation in a twisted nematic liquid crystal (TNLC) SLM using a double pass technique. A Jones calculus model is developed which matches our experimental data.     

丝状相液晶由表面相互作用产生的相变

导出双轴丝状相液晶在指向矢与易取向轴重合时的表面相互作用能.应用Ritz方法,对半无 界液晶体得出沿表面法向的双轴相(B_c)至沿表面某一轴的双轴相(B_a)的相变.随着表面锚泊强度双轴性部分的增大,B_a的产生机制逐渐由降低温度 转为表面锚泊,因此B_a相可出现在较高温度和较大温度范围内.在表面锚泊强度 单轴性部分α值的一定范围内,增大α值可使B_a在较高温度产生,但α值的进 一步增大则使液晶又从B_α返回B_c相. 关键词： 液晶 相变 表面能     

扭曲向列相液晶电光效应的微观机理研究

为了探究液晶电光效应的微观机理,以扭曲向列相液晶为研究对象,对液晶分子的变化情况进行了理论分析。运用连续体弹性理论分析了扭曲向列相液晶分子的指向矢取向变化,并对液晶电光效应曲线不同区间范围液晶微观结构的变化进行了系统分析。结果表明:液晶分子在零电场条件下的扭曲是均匀的;当外加电场大于某一值时,液晶分子开始转向,液晶产生电光效应。研究结果对液晶显示器件设计和深入理解液晶电光效应机理具有一定的指导意义。     

表面液晶-垂直腔面发射激光器温度特性的研究

本文利用向列相液晶层作为激光偏振调控单元,涂覆于垂直腔面发射激光器（VCSEL）表面,测量并分析了不同温度下VCSEL正交线偏振光的阈值电流、峰值光功率和I-P特性. 实验结果表明：温度为293 K时,涂覆液晶后激光偏振第一跳变点和第二跳变点之间的电流值ΔI增大了2.2 mA,比无液晶时增大1倍. 温度为313 K、注入电流为3 mA时,两种正交线偏振光的光功率差ΔP由133.6 μW增大到248.8 μW,进一步增加了线偏振光的各向异性. 表面液晶层的引入有效地扩大了VCSEL的正交线偏振态稳定范围和光功率差,为实现液晶VCSEL高温单偏振稳定的设计和器件制备提供了理论和实验基础. 关键词： 垂直腔面发射激光器 向列相液晶 偏振态     

Phase-Only Modulation with a Twisted Nematic Liquid Crystal Panel for a Reconfigurable Grating

A single-path transmission type twisted nematic liquid crystal panel appears to achieve nearly phase-only spatial light modulation when placed between a properly aligned polarizer and analyzer. We obtained more than π phase delay with the equipment whose retardation was less than π.     

Lattice Boltzmann Simulation of 3D Nematic Liquid Crystal near Phase Transition

Phase transition between nematic and isotropic liquid crystal is a very weak first order phase transition.We avoid to use the normal Landau-de Gennes‘s free energy that reduces a strong first order transition,and set up a data base of free energy calculated by means of Tao-Sheng-Lin‘s extended molecular field theory that can explain the experiments of the equilibrium properties of nematic liquid crystal very well.Then we use the free energy method of lattice Boltzmann developed by Oxford group to study the phase decomposition,pattern formation in the flow of the liquid crystal near transition temperature.     

High Efficiency Electrically-Addressable Phase-Only Spatial Light Modulator

To realize a high efficiency electrically addressable phase-only modulator, we have coupled a liquid crystal display (LCD) to an optically addressed parallel-aligned nematic liquid crystal spatial light modulator (PAL-SLM) with a set of lenses. Phase modulation exceeding 3ϖ at 532 nm wavelength was obtained. We obtained linear transfer characteristics for phase modulation at various desired phase levels after calibration and adjustment of the transfer characteristics of the PAL-SLM and the LCD. Diffraction efficiency of 40% for binary phase grating and of 90% for 8-level blazed phase grating, which were very close to the simulation values, were observed. The power loss of the readout light was caused when passed through a half mirror, therefore, we examined a setup using an oblique readout light at the modulator. Very high diffraction efficiency was obtained from the setup by optimizing the polarization direction and optical path for this light, and the orientation of liquid crystals. Since the modulator can perform at better than 90% diffraction efficiency and at nearly 100% reflectivity, various high efficiency systems utilizing such modulators are expected.     

Phase Conjugation by Degenerate Four-wave Mixing in Nematic Liquid Crystals

1.IntroductionOpticalphaseconjugationhasbeeninvestigatedextensivelybecauseofitswideapplicationsinimagingtechnology,phase--conjugationlasers,andopticalassociativememorysystems.Notedfortheirlargeopticalreorientationnonlinearities[IJ,nematicliquidcrystals(NLC)havebecomepromisingopticalmediaforapplicationsinthefieldofnonlinearopticsincludingnonlinearphaseconjugation.In1980,Feketectal.[2)firstrealizedphase--conjugationbydegeneratefour--wavemixing(DFWM)inNLCintheisotropicphase.Sincethen,thefie…     

平行式向列液晶实现相移剪切电子散斑干涉术的研究

研究了向列型液晶的相位调制特性，采用平行式向列液昌作为相移器建立了相移剪切电子散斑干涉计量系统。该方法将相移技术引入到剪切电子散斑干涉术中，提高了检测精度，采用了相关条纹法求解相位，简化了计算；相移方法简单，可靠。用该系统进行应变场的测量实验，取得了满意的效果。     

液晶电光特性研究

随着近几年液晶显示技术在诸多领域的广泛应用和新技术的推出,人们一直致力于改善液晶器件显示性能的研究。在液晶显示器应用中,电光特性是一个很重要的参数,介绍了采用激光测量的方法获得液晶的电光特性、阈值电压及视角特性。分析了液晶分子在交流电场作用下重新取向后的扭曲特性,测试了不同电压下液晶分子的透光率和扭曲角度,结果表明:该方法是可行的,向列相液晶具有0.92 V较低阈值电压和较为陡峭的电光曲线,水平方向上在-60~+50有较好的视角特性,垂直方向上在-40~+20有较好的视角特性。该结论为偏光器件的设计与制作提供了依据。     

Oblique-Incidence Characteristics of a Parallel-Aligned Nematic-Liquid-Crystal Spatial Light Modulator

We have developed optically-addressed and electrically-addressed liquid crystal spatial phase-only light modulators having no pixelized structures. We obtained a large depth of phase-only modulation and high diffraction efficiency based on the electro-optical characteristics of a parallel-aligned nematic liquid crystal. These spatial light modulators (SLM) are of the reflection type, so there would be a loss of power in the readout light from the half mirror, which was set up so as to separate the incident and reflected lights. To optimize the characteristics of a reflection type spatial phase-only light modulator, we have proposed an oblique incident optical readout setup. We have examined the effect of conditions such as the polarization direction and the incidence angle of the readout light, and the orientation of liquid crystal molecules in the SLM. High diffraction efficiency close to the theoretical maximum value was obtained by adjusting the above conditions. The simulation analysis can well explain the experimental results of phase modulation.     

Genetic optimization of modulation characteristics for two twisted nematic liquid crystal spatial light modulators

A single twisted nematic liquid crystal spatial light modulator may suffer from coupled amplitude modulation and a phase modulation capability of less than 2, although almost all panels can achieve . Two twisted nematic liquid crystal panels can be combined in an optical system to produce a total phase modulation of at least 2, and a minimal coupled amplitude modulation. A genetic algorithm is used to optimize the combined modulation characteristics of two liquid crystal panels in a multiplicative architecture. Simulation results and experimental verification are presented which show a substantial reduction in the combined amplitude modulation, and a total phase modulation of 2.     

Electrically-Controllable Liquid Crystal Polarizing Filter for Eliminating Reflected Light

A high-speed controllable polarizing filter has been developed to eliminate obstructive polarized light reflected from glass and watery surfaces for image pickup in video media program producing and marine dynamic remote sensing. In this device, the polarization plane of incident light is rotated through 0°, 45°, 90° or 135° by an electrically-controllable polarization rotator composed of 45° and 90° twisted nematic liquid crystal cells, and the polarization component of reflected light is absorbed by a fixed polarizing film. It selectively absorbs more than 80% of incident white light linearly polarized in an arbitrary direction. With the drastic reduction of reflected light, the object images hidden by the bright reflected light are clearly captured in real time. Another type of polarizing filter, using a guest-host liquid crystal cell instead of the polarizing film, controls light absorption as well as polarization angle.     

平行排列丝状液晶在超短脉冲激光激励下发生瞬态扭曲形变的最佳偏振角

利用光学相位延迟法，观察到平行排列丝状液晶在超短脉冲激光（10ns）激励下的瞬态扭曲形变.实验结果表明，虽然脉冲激光的电场强度远远大于液晶发生扭曲形变的阈值，但并不能保证液晶会发生瞬态扭曲形变.这主要是因为脉冲激光的激励时间非常短，而液晶分子发生扭曲形变的响应时间相对较长，从而使其来不及形变.分析发现：激励激光的偏振方向与平行排列丝状液晶分子的最佳夹角是45°.利用此条件，观察到掺微量D型苏氨酸卟啉的平行排列丝状液晶在超短脉冲激光激励后具有记忆效应，这在光存储和记忆显示方面有很大的实用价值.