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1.
马骥  郑致刚  刘永刚  宣丽 《中国物理 B》2011,20(2):24212-024212
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.  相似文献   

2.
全息聚合物弥散液晶器件电光特性的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
张斌  刘言军  徐克璹 《物理学报》2004,53(6):1850-1855
研究了全息聚合物弥散液晶(HPDLC)器件的电光特性,研究了添加不同表面活性剂对聚合物界面对液晶的锚定能的影响机理,寻求到了低工作电压的实现方法. 分析了聚合物基体与液晶折射率不匹配性对器件对比度的影响,测量了HPDLC器件的响应时间和弛豫时间,得到了平均100μs的快速响应. 关键词: 全息聚合物弥散液晶 电光特性 表面活性剂 对比度 响应时间  相似文献   

3.
Diffraction of liquid crystal gratings has been thoroughly studied for many applications such as diffraction optics, optical processing, and spectral analysis. In pure optical processing one varies the direction of propagation of light beam without any mechanical adjustment. In this work we propose a beam steering device using highly birefringent liquid crystal material. Using a highly birefringent material one can reduce the LC layer thickness needed to achieve 2π of phase modulation and thus reduce the fringing effect caused by deformation of the electric field at the edge of the pixel. Here, we present 1.5-μm thick, high-resolution diffraction grating with non-detectable fringing.  相似文献   

4.
Low viscosity, high birefringence liquid crystalline compounds and mixtures   总被引:1,自引:0,他引:1  
Two types of fast switching mixtures with high positive dielectric anisotropy were described. The first type, with a birefringence below 0.3, was designed for devices operating at room or lower temperatures and the second one, with a birefringence higher than 0.3 for devices operating at elevated temperatures.  相似文献   

5.
We have experimentally studied for the first time the electro-optical Kerr effect and the pre-transitional behavior in the isotropic phase of two antiferroelectric liquid crystal mixtures, W-232 and W-204D, composed of rod-like ester molecules exhibiting the direct smectic-A to isotropic (SmA-I) phase transition. The Kerr law has been confirmed for the two compounds and the variation of inverse Kerr constant with temperature above the smectic–isotropic transition temperatures were determined. Both the mixtures with very broad antiferroelectric phase around room temperature have similar sequence of the phases (i.e., Cr-SmC*A-SmC*-SmA-I). Although, the pre-transitional behavior is usually complex in the isotropic phase of the chiral smectic liquid crystal compounds, the investigated compounds showed a similar behavior compared to that of nematic–isotropic behavior.  相似文献   

6.
V形高双折射光子晶体光纤特性研究   总被引:1,自引:0,他引:1       下载免费PDF全文
夏长明  周桂耀  韩颖  刘兆伦  侯蓝田 《物理学报》2011,60(9):94213-094213
本文基于全矢量有限元法,设计了一种V形结构高双折射光子晶体光纤,数值分析结果表明:当光纤的包层孔间距Λ为1.0 μm,包层大空气孔D和小空气孔d分别为0.95 μm,0.7 μm时,在波长为1.55 μm处,该光纤的双折射度B达到1.225×10-2,比传统光纤高约两个数量级. 另外,分别在可见光和近红外波段出现了两个零色散波长,使钛宝石飞秒激光器工作波段(700—980 nm) 处于光纤的反常色散区,为新颖的光子晶体 关键词: 光子晶体光纤 高双折射 有限元法 V形结构  相似文献   

7.
赵原源  周桂耀  李建设  韩颖  王超  王伟 《物理学报》2013,62(21):214212-214212
高非线性高双折射光子晶体光纤是超连续谱产生的最有效介质之一, 因此本文选取V型光子晶体光纤作为研究对象. 通过多极理论数值模拟的结果, 确定V型光纤具有高双折射、高非线性等特性. 通过实验手段, 发现入射光中心波长和光纤的双折射效应对产生的超连续谱有很大的影响: 当入射光波长处于光子晶体光纤大的反常色散区时, 脉冲相对展得比较宽, 长轴要比短轴方向的超连续谱更宽, 频谱成分更加丰富. 在同一波长下光偏振方向越接近45°时, 超连续谱谱宽范围越大. 随着入射脉冲功率的增加, 超连续谱展得越宽, 但是当功率比较大时会达到功率饱和. 关键词: 光子晶体光纤 高双折射 多极理论 超连续谱  相似文献   

8.
In this work we have used acetoxypropylcellulose (APC) to produce free standing solid films (∼60 μm) that were used for assembling electro-optical devices. Thin films were obtained from concentrated lyotropic solutions of cellulose derivatives. Induced by the cast and shearing preparation conditions wrinkles and band textures can be observed in their free-surface plane. In order to eliminate and control these textures we used a process similar to that introducted in literature [1] which consists of storing the films in the same solvent-vapour atmosphere as the solution system. Lyotropic APC liquid crystalline solutions in dymethylacetamide (DMA) with crosslinker were prepared, thin films were obtained by using a shear/casting technique and stored in the solvent-vapour atmosphere until a planar structure was achieved. The dried crosslinked films were analyzed by optical polarised microscopy (POM) and scanning electron microscopy (SEM). The films with different topographies were used to produce optical cells composed by the cellulose derivative film covered on both free surfaces by a layer of the nematic liquid crystal E7 and placed between two transparent conducting substrates. The electro-optical properties of these cells were obtained.  相似文献   

9.
A doubly fluorinated isothiocyanato butyl terphenyl compound exhibiting a broad range of the nematic and a narrow range of smectic phase has been investigated by X-ray, dielectric and optical methods and compared with the properties of singly and doubly fluorinated ethyl homologues to see the effect of fluorination and chain flexibility. Contrary to common perception, weak antiparallel correlation of molecules is observed in each compound both from X-ray and dielectric studies. Observed dielectric anisotropy is strong enough to ensure a driving voltage suitable for thin film transistor-based liquid crystal display. Measured splay elastic constant suggests that the present compound will exhibit the fastest response. Flip-flop mode relaxations are observed in a few hundred kHz to MHz range. All the compounds exhibit high birefringence (0.373–0.331). They also show high order parameters at low temperatures. These compounds are expected to be suitable for formulating high birefringence nematic mixtures for fast switching displays.  相似文献   

10.
Photonic liquid crystal fibers have already been demonstrated as a promising perspective for creation of new classes of dynamically tunable optical fiber devices. By combining different geometries of photonic crystal fibers with a variety of different liquid crystals it is possible to obtain a new generation of fibers with dynamically tunable properties, e.g., transmission spectra, attenuation or dispersion. In this paper, tunable birefringence in a commercially available highly birefringent Blazephotonics PM-1550-01 photonic crystal fiber selectively filled with a low birefringence liquid crystal has been experimentally demonstrated. Theses experimental results have been compared with simulations based on the multipole method.  相似文献   

11.
A theory is developed of the anomalous magnetic and electric birefringence in the isotropic phase of nematic liquid crystals taking into account orientational correlations between neighbouring molecules. Use is made of a modification of Bethe’s method due to Krieger and James, and the properties of the system are derived in terms of a single parameter, viz., the two-particle interaction constant. The expressions for the magnetic and electric birefringence are similar in form to those given by the phenomenological model of de Gennes. Theoretical curves forp-azoxyanisole reproduce the trends in the observed data. A calculation of the nematic-isotropic transition point confirms that this treatment is an improvement over the mean field approximation in describing pre-transition phenomena in the isotropic phase.  相似文献   

12.
The paper reviews and discusses the latest developments in the field of the photonic liquid crystal fibers that have occurred for the last three years in view of new challenges for both fiber optics and liquid crystal photonics. In particular, we present the latest experimental results on electrically induced birefringence in photonic liquid crystal fibers and discuss possibilities and directions of future developments.  相似文献   

13.
一种新型高双折射光子晶体光纤特性研究   总被引:4,自引:0,他引:4       下载免费PDF全文
曹晔  李荣敏  童峥嵘 《物理学报》2013,62(8):84215-084215
设计了一种高双折射高非线性光子晶体光纤, 采用全矢量有限元法研究了这种光纤的基模模场、双折射、非线性、有效模面积及色散特性. 数值研究发现, 减小孔间距Λ的大小, 在波长1550 nm 处, 该光纤可获得10-2 数量级的双折射B, 比普通的椭圆保偏光纤高约两个数量级; 同时, 该光纤可获得42 W-1·km-1 的高非线性系数γ. 另外,分别在可见光和近红外波段出现了两个零色散波长, 在波长800–2000 nm 之间具有良好的色散平坦特性. 这种设计为获得高双折射高非线性超平坦色散光子晶体光纤提供了一种新的方法, 该光纤在偏振控制、非线性光学和色散控制方面具有广泛的应用前景. 关键词: 光子晶体光纤 高双折射 高非线性 有限元法  相似文献   

14.
高双折射纳米结构光子晶体光纤特性研究   总被引:3,自引:0,他引:3       下载免费PDF全文
张磊  李曙光  姚艳艳  付博  张美艳  郑义 《物理学报》2010,59(2):1101-1107
设计了一种高双折射高非线性纳米结构光子晶体光纤,利用电磁场散射的多极理论研究了这种光纤的双折射、基模模场、色散以及非线性特性.数值研究发现,加大纤芯及包层空气孔的非对称程度,可使双折射变大,其双折射最大值可达1.918×10-2.通过调节孔节距大小,可将双折射最大值调至所需波长处,孔节距为400nm的纳米光子晶体光纤在800nm波长处非线性系数高达0.2m-1.W-1,同时在750—1000nm的波段有较大的双折射值,高双折射和高非线性在纳米结构光子晶体光纤中实现了完美的结合.对新型纳米光子器件的研制和集成光学的发展具有重要意义.  相似文献   

15.
剪切聚合物分散液晶散射偏光特性   总被引:10,自引:2,他引:10  
介绍了拉伸聚合物分散液晶和散射偏光片概念,实验制备了剪切聚合物分散液晶样品,给出了对聚合物分散液晶样品施加剪切应力的偏光特性光谱分析.实验结果表明,吸收偏光片前置和后置样品的散射偏光效果相同,样品在绿光550nm波长处最大透光率T//~60%,最小透光率T┴~10%,偏振度P~70%.实验结果对于其他散射偏光片具有普遍...  相似文献   

16.
Graphene oxide (GO) particles in aqueous dispersions can form liquid crystal (LC) phases at extremely low concentrations due to the extremely high aspect ratio of the flakes and noticeably, they possess an extremely large Kerr coefficient attractive for low power consumption electro‐optic devices. Reduced graphene does not easily form LC phases in water due to its hydrophobic nature but here we show that stable dispersions of reduced graphene oxide can be realized with surfactants and that they exhibit birefringence upon shearing as well as under application of electric fields. The performance of the system is largely superior to GO LC possessing longer time stability and drastically improved electro‐optic properties with an induced birefringence twice as large at the same field strength thanks to the almost recovery of graphene properties upon reduction. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)  相似文献   

17.
用平面波展开法对光子晶体光纤中电磁场的Maxwell方程组进行了求解。将光纤截面作为超元胞衍生出一个无边界的二维周期性系统,光纤纤芯等效为光子晶体中的缺陷,借助平面波法对其性质进行研究,模拟了半导体中的超格子。运用上述超格子模型,对与纤芯同列孔半径可变的高双折射及与包层中纤芯距离最近的孔半径可变的色散平坦光子晶体光纤的光学性质进行了研究,发现与纤芯同列的孔半径变化时,其双折射比传统光纤更强,而当包层中距离纤芯最近的孔半径取特定值时,可得到近零色散平坦光纤并在大范围内获得反常色散。与传统光纤和普通光子晶体光纤相比,这种新型的色散平坦光纤在密集波分复用(DWDM)光通信系统中具有更高的应用价值。  相似文献   

18.
一种新型高双折射光子晶体光纤   总被引:2,自引:0,他引:2       下载免费PDF全文
张晓娟  赵建林  侯建平 《物理学报》2007,56(8):4668-4676
提出了一种新的高双折射光子晶体光纤结构.应用全矢量频域有限差分方法所做的数值分析表明:该结构光纤基模的两个正交偏振态不再简并,其模式呈现很强的线偏振特性,并且模式双折射与结构参数设置有密切关系.通过选择合适的结构参数,可以使之达到10-2量级,比传统的D型和熊猫型保偏光纤高出2个数量级.合理设计光纤包层的几何结构,可以取得理想的色散效果.这种结构的光子晶体光纤可用于制作具有适当色散特性或偏振特性的保偏光纤及相关光纤器件. 关键词: 光子晶体光纤 模式双折射 偏振特性 频域有限差分法  相似文献   

19.
In this paper, a highly birefringent index-guiding photonic crystal fiber with low confinement loss is proposed by enlarging the central row of air holes in the structure. By employing the multipole method, properties of this structure, including the effective index, birefringence and confinement loss, are investigated. Simulation results indicate that high birefringence of 1.65 × 10−3 can be reached at the wavelength of 1.55 μm, and a low confinement loss on the order of 10−6 dB/km can be achieved at the same wavelength. Moreover, the impacts of air hole sizes on birefringence and confinement loss are also analyzed in detail.  相似文献   

20.
In this paper we present numerical and experimental results of propagation and polarization properties of the photonic liquid crystal fibers (PLCFs) in which only selected micro holes were filled with nematic liquid crystal (LC) guest materials. As a host photonic crystal fiber (PCF) structure, we used a commercially available highly birefringent PCF (Blazephotonics, UK). A tunable laser operated at infrared has powered the PLCFs under investigation infiltrated by the 1550 nematic LC synthesized at the Military University of Technology. Temperature induced changes of the polarization mode dispersion (PMD) as well switching between fundamental and higher order modes and also single-core and two-core propagation were successfully demonstrated.  相似文献   

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