偶氮侧链聚合物液晶的光学性质及其光存储应用

有机聚合物是一类非重要的非线性光学材料，它在光通信和高密度光存储等高技术领域中有良好的应用前景，文章介绍了偶氮侧链聚合物液晶的光学性质及其在光存储领域中的应用。     

偶氮液晶聚合物中的非线性光致双折射

介绍了在偶氮液晶聚合物薄膜P-CN中发现的非线性光致双折射现象,给出了非线性光致双折射实验的具体结果.采用Z扫描技术验证了光致双折射的非线性过程本质,测量了P-CN介质薄膜的非线性吸收系数.讨论了光致双折射涉及的异构化微观机理,并在此基础上提出了非线性光光异构化实现光致双折射的方法 关键词： 液晶聚合物 光致双折射 光致异构化     

聚合物网络稳定液晶的电光偏振片

制备了一种散射偏振片,它是由非晶态单体形成的聚合物网络、向列液晶和涂有聚酰亚胺的ＩＴＯ玻璃基板组成。聚酰亚胺被反向平行摩擦,液晶分子则沿摩擦方向取向,并被单体形成的网络所稳定。根据聚合物网络液晶的电光特性可知。入射偏振光束被散射或透射相应地取决于其偏振方向平行还是生趣于基板的摩擦方向。平行时,光的散射强度通过电场可被强烈地调节;垂直时,光的透过率很高,几乎不依赖施加的电场。这种偏振器件具有低的驱动     

表面摩擦处理对全息聚合物分散液晶光栅电光特性的影响

为了提高全息聚合物分散液晶光栅的衍射效率并降低其驱动电压,改善光栅的电光特性,研究了表面平行摩擦取向对全息聚合物分散液晶光栅电光特性的影响.理论分析认为,改善相分离结构和降低液晶微滴之间的有序度差异是优化光栅电光特性的根本所在.由于进行表面取向处理后的液晶和单体之间达到扩散匹配,使得相分离的程度大幅提高,在衍射能力增强的同时驱动电压也实现了大幅下降,而且,表面取向作用也使光栅内的液晶分子均匀排列,降低了液晶微滴之间的有序度差异,从而减少了光栅的散射损失.实验结果表明:进行取向处理后的光栅其衍射效率由传统光 关键词： 全息聚合物分散液晶 衍射效率 驱动电压     

新型聚合物分散液晶相位光栅的制备

把具有光敏特性的预聚物与向列相液晶按一定比例混合 ,注入表面经过取向处理的液晶盒中。以紫外灯为光源 ,通过光掩膜法 ,使混合物在光场的引发下发生相分离 ,形成液晶 /聚合物相位光栅。由于相分离后液晶在取向膜的作用下沿液晶盒面方向旋转 180° ,克服了传统液晶光栅器件对入射光偏振方向的依赖 ,提高了光的有效利用率。采用光学显微镜和He Ne激光器进行测试 ,结果表明所制样品具有较好的栅结构 ,其衍射效率不受入射光偏振方向的影响且具有电场可调性。该光栅制作方法简便 ,驱动电压低 ,在光通信器件、衍射光学、投影显示、光开关等领域有广泛的应用前景     

用偏光显微术研究聚合物分散液晶压光效应膜

制备出大液晶微滴的具有压光效应的聚合物分散液晶膜,给出样品按压前后偏光显微镜对比照片.提出压缩液晶微滴模型,采用Fortran软件模拟计算了压光效应液晶微滴双折射透光率分布,用Origin软件作图,计算结果绘图与偏光显微镜图片一致.定义按压后液晶微滴圆球变扁球的扁平度,计算按压后序参数与扁平度的关系,说明按压作用使液晶...     

用于电响应红外反射窗的液晶聚合物薄膜特性研究

提出了一种红外反射器件,通过载体液晶在电场下的转向控制胆甾型液晶聚合物粒子在器件中的排布方向,实现红外反射与透射之间切换.其中,胆甾型液晶聚合物粒子是实现红外反射关键.介绍了胆甾型液晶聚合物薄膜的制备方法,并采用超声波破碎的方法制备液晶粒子.研究了液晶混合物中不同比例的交联剂液晶1对液晶聚合物薄膜脆性和反射波段的影响,发现当液晶1占100%时,液晶聚合物薄膜的脆性最大,且其清亮点最高,并且薄膜的反射波段随着液晶1比例的增加而向短波方向偏移.同时,研究了薄膜厚度对液晶聚合物粒子的影响,发现液晶薄膜厚度越小,制备的液晶聚合物粒子越小且越均匀,其制成的器件电驱动性更好.该研究有利于帮助电响应红外反射窗的性能优化.     

基于聚合物支撑形貌液晶/聚合物光栅的低阈值分布反馈式激光器

利用低光强曝光进行全息液晶/聚合物光栅(HPDLC)的制备,获得了内部无液晶微滴具有聚合物支撑形貌的低散射透射光栅结构.分别研究了染料PM567,DCM,DCJTI的放大的自发辐射(ASE)阈值及相对出射光强等性质,得到三种染料中DCJIT的ASE阈值最低,相对出射光强最高,表明DCJTI更适于制备低阈值、高转化效率激光器.分别采用这三种染料制备基于聚合物支撑形貌光栅的分布反馈式激光器,通过改变光栅周期得到不同出射波长的激光.其中,以DCJTI为工作物质,得到中心波长为648 nm,阈值为0.65μJ/pulse,转化效率为1.6%,线宽为0.3 nm的高性能激光.与国内外同类激光器相比,在阈值、转化效率、线宽三个方面均有不同程度的提高.     

Random lasing in dye-doped polymer dispersed liquid crystal film

A dye-doped polymer-dispersed liquid crystal film was designed and fabricated,and random lasing action was studied.A mixture of laser dye,nematic liquid crystal,chiral dopant,and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules.Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm,the size of the liquid crystal droplets was small.Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation,a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575–590 nm.The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 m J.Under heating,the emission peaks of random lasing disappeared.By detecting the emission light spot energy distribution,the mechanism of radiation was found to be random lasing.The random lasing radiation mechanism was then analyzed and discussed.Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism.The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small,which is beneficial to form multiple scattering.The transmission path of photons is similar to that in a ring cavity,providing feedback to obtain random lasing output.     

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.     

‘Guest–host’ effect in liquid crystal mixtures

The most important goal of our research is to show the influence of the ‘guest’ (bent-core mesogen, 1,3-phenyldicarboxylatebis{4-[(4-octylbenzoyl)sulphanyl]phenyl} [IFOS8], banana-shaped liquid crystal [BLC]) on the ‘host’ (calamitic liquid crystal [CLC], (S)-(+)-1-methylheptyloxybiphenyl-(4-n-octylphenyl)thiobenzoate [MHOBS8]), on the stability and the destabilization of the antiferroelectric B2 and the ferroelectric smectic C* (SmC*) phases, and change of the temperature ranges of other phases in the binary liquid crystal mixtures. This work is focused on polymorphism of three new binary liquid crystal mixtures, exhibiting a ‘guest–host’ (guest liquid crystal–host liquid crystal [GH-LC]) effect. MHOBS8 has, among others, a ferroelectric SmC* phase, and IFOS8 assumes the B2 phase with antiferroelectric properties. The observed properties of the mixtures, such as variation of the phase transition temperatures, spontaneous polarization, tilt angle and switching time, are characteristic of a ‘guest–host’ mixture. The influence of BLC on the character of the interactions within the CLC host is discussed, with particular attention paid to electro-optical properties of the GH-LC mixtures.     

应变液晶散射偏光片的试制

介绍了聚合物分散液晶(PDLC)和应变液晶(SLC)以及散射偏光片的概念,实验制备了应变液晶散射偏光片样品,样品由两张胶片夹层聚合物分散液晶膜在紫外光固化过程中施加剪切应力所形成。给出了样品偏光显微镜照片和可见光分光光度计偏光特性光谱分析。实验结果表明,应变液晶散射偏光片样品外观半透明,在正交偏光场中转动样品有颜色变化,通过样品观察液晶显示器屏幕,在不同角度下有透射和散射作用,在偏光显微镜中观察样品有衬垫料被拉动的痕迹,光谱分析显示样品在绿光550nm波长处最大透光率T∥≈50%,最小透光率T⊥≈5%,偏振度P≈82%。实验结果对于研制实用的拉伸液晶散射偏光片具有参考意义。     

液晶磁致旋光的研究

利用矩阵方法分析了液晶的旋光效应，导出了液晶旋光的矩阵表示. 利用JG-3型连续可调谐磁场仪搭建实验装置，红外1350 nm激光器做光源，测量了偏振光通过磁场作用下BL-009型向列相液晶的旋光角，详细分析了磁场对液晶旋光性能的影响. 通过实验测试，对液晶的阈值磁场强度进行了讨论，同时对实验结果进行了理论上的分析，得出了液晶旋光角随磁场与液晶盒表面夹角而变化的结论，验证了液晶分子轴的旋转方向与磁场的方向无关，这为更好的研究液晶的特性以及液晶器件的设计具有重要的参考价值. 关键词： 液晶 矩阵 磁致旋光     

Diffraction Properties of Field Adjustable Polymer Network Stabilized Liquid Crystal Grating

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Diffraction Properties of Field-Adjustable Polymer Network Stabilized Liquid Crystal Grating

A new diffraction grating mode has been proposed. This grating is formed by applying of a spatially periodic electric field to a polymer network stabilized uniformly aligned liquid crystal layer. Due to the electro-optic properties of the polymer network stabilized liquid crystal layer, the grating type is electrically adjustable, i.e. it presents amplitude, phase or amplitude-phase type depending on the applied voltages. Experimental results show that the number of visible diffraction orders can be adjusted easily, and even be closed at the same time. The detail fabrication process and experimental results will be presented.     

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。     

基于丙烯酸酯的全息聚合物分散液晶光栅的动力学理论研究

采用一维无限长模型分析法对全息聚合物分散液晶(HPDLC)做了动力学方面的研究，给出了相关的扩散动力学方程和聚合动力学方程,并与折射率调制度Δn相结合获得了光栅衍射效率的表达式，对HPDLC光栅性能的改善提供了理论上的指导.     

Electro-optical properties cholesteric liquid of polymer stabilized crystal film＊

Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.     

Electro-optical properties of polymer stabilized cholesteric liquid crystal film

Liquid crystals (LCs) and polymers are extensively used in various electro-optical applications.In this paper,normal mode polymer stabilized cholesteric LC film is prepared and studied.The effects of chiral dopant and monomer concentrations on the electro-optical properties,such as contrast ratio,driving voltage,hysteresis width and response time,are investigated.The reasons of electro-optical properties influenced by the concentrations of the materials are discussed.Through the proper material recipe,the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.     

基于低散射和高增益全息液晶/聚合物光栅的分布反馈式激光器

利用低官能度的丙烯酸酯单体进行全息液晶/聚合物光栅的制备, 获得了具有聚合物支撑形貌的光栅结构. 由于这种光栅内部不存在液晶微滴, 当作为分布反馈式激光器的谐振腔时, 可以有效降低光栅内部的散射损失(<4%), 降低激光腔损耗. 此外, 选用的高折射率单体提升了光栅的折射率调制量, 增强了光栅的反馈增益. 在以上两种因素的共同作用下, 采用染料DCM为激光工作物质, 以532 nm的Nd:YAG脉冲激光器作为抽运光源, 最终获得了中心波长为635 nm, 转化效率为1.2%的高性能激光, 在以阈值能量0.8 μJ/pulse抽运下获得激光线宽0.3 nm, 较之国内外同类激光器的报道, 在阈值、线宽、转化效率三方面均有不同程度提升.