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1.
We present a detailed theoretical analysis and experimental study of purely optically-induced nematic axis reorientation and the associated nonlinear optical processes such as self-phase modulations and optical switching. It is shown that under a sufficiently intense laser field (∼ 100 MW/cm2), nematic liquid crystals will respond in the nanosecond regime. Single nanosecond laser pulse self-phase modulation and intensity switching effects are observed. The magnitude and dynamics of the response are in agreement with theoretical expectations. Optical power limiting and switching effects associated with self-phase modulations are also demonstrated.  相似文献   

2.
The dynamic self-diffraction effects due to large optical nonlinearities of nematic liquid crystals via molecular reorientation are reviewed. The laser-induced gratings are shown to arise because two waves with ordinary and extraordinary polarizations propagate in a nonlinear anisotropic medium. Both threshold and thresholdless effects as well as nonlinear scattering in an initially nonhomogeneous medium are discussed. Direction of further work in this field as well as potential applications are indicated.  相似文献   

3.
The origins and the dynamics of optical nonlinearities in nematic liquid crystal films, namely, laser-induced molecular reorientational and thermal refractive index changes, are analyzed in the context of optical wave mixings. Theoretical expressions for the basic non-linearities, the rise and decay time, diffraction efficiencies, and other pertinent parameters involved in the dynamic grating formation are derived. Experimental results obtained with visible and infrared laser pulses are analyzed. Some newly observed novel nonlinear processes are also reported.  相似文献   

4.
可调光子晶体由于其潜在的应用价值成为现今光子晶体研究中的一个热点。文章首次提出了通过光诱导液晶取向技术来调制光子晶体光子禁带的方法,进而采用平面波展开法分析了填充液晶的二维三角形光子晶体禁带结构的可调节性。数值模拟结果表明:通过偏振光控制空气孔中所填充的相列液晶的方向可以对光子晶体的禁带结构进行调节。与电场调制方法相比,该光控液晶取向技术具有响应速度快、结构简单的优点。这种可调光子晶体可用于制作场敏偏光片、全光光开关和可调光衰减器。  相似文献   

5.
陈书潮  陈浚波 《中国激光》1990,17(9):553-558
报道了国产向列型液晶MBBA和EBBA的Raman谱与温度的关系。提出了一种适用于取向的向列型液晶分子振动相关函数和转动相关函数的分离理论。此理论应用于MBBA液晶相和液相的分子振动和转动弛豫的实验研究表明这种分离方法是可行的。  相似文献   

6.
聚合物网络对液晶的表面作用决定了聚合物稳定向列相液晶的电光性能。我们的研究基于一种简单的表象模型,假设聚合物网络由平行于无场状态下向列指向矢的聚合物纤维棒构成。建立受到有限锚定能虚拟边界束缚的矩形指向矢畴,根据液晶的动力学理论得到聚合物稳定向列相液晶显示的上升时间常数的表达式。计算并给出了上升时间常数对聚合物浓度的依赖关系,此关系还有待于实验的验证。  相似文献   

7.
基于电磁感应透明的弱光非线性研究进展   总被引:1,自引:0,他引:1  
利用电磁感应透明实现弱光场条件下的强非线性效应,开辟了一个崭新的非线性光学研究领域-“弱光非线性光学”。主要介绍了基于电磁感应透明的Kerr非线性和四波混频效应。Kerr非线性在全光学开关、全光学逻辑运算和光量子逻辑门等方面有着潜在的应用价值。四波混频也具有非常广泛的应用,其中最重要的是把可调谐相干光源的频率范围扩展到红外和紫外。在简并情况下,四波混频对于自适应光学中的波前再现是很有用的。另外,在材料研究中共振四波混频技术是强有力的光谱分析工具。  相似文献   

8.
弯曲型向列相液晶研究进展   总被引:3,自引:3,他引:0  
弯曲型向列相液晶是近年来新发现的一类具有特殊光电性能的液晶材料。这类液晶分子具有独特的弯曲形状,表现出不同于棒状液晶的优良特性;但这些弯曲型向列相液晶分子普遍存在着熔点高,易出现宽温近晶相的问题。文章对以取代间苯二酚、萘环、噁二唑环等为中心环,酯键、碳(氮)氮双键等为桥键的弯曲型向列相液晶化合物的分子结构、特性、研究进展以及侧位取代对液晶性能的影响做了简要概述。  相似文献   

9.
We have constructed an optical fiber switch, which allows to route an information carrying laser beam to nine multimode optical fibers. The fibers are accurately positioned in a polymethylmethacrylate (PMMA) fiber array holder, fabricated with deep proton lithography. To switch light from one fiber to another, we use active control of the polarization of light by means of nematic liquid crystal retarders or ferroelectric polarization rotators. The system shows insertion losses as low as 3 dB and crosstalk ratios below -30 dB. These figures are still susceptible to considerable improvements. The switching speed is on the order of 10 Hz using nematic liquid crystals and was extended to 10 kHz with ferroelectric liquid crystals. Potential applications of the fiber switch are discussed. As an illustration we have demonstrated the multiplexing of optical fiber proximity sensors. We also describe scale reduction and cascadability issues  相似文献   

10.
Fascinating nematic‐ and smectic‐like self‐assembled arrays are observed for gold nanorods partially capped with either laterally or terminally attached nematic liquid crystals upon slow evaporation of an organic solvent on TEM grids. These arrays can be manipulated and reoriented by applying an external magnetic field from quasi‐planar to vertical similar to a Fréedericksz transition of common organic nematic liquid crystals. Birefringence and thin film textures of these self‐assembled gold nanorod arrays observed by polarized optical microscopy are strongly reminiscent of common organic nematic liquid crystal textures between crossed polarizers and, additionally, support the formation of ordered liquid crystal‐like anisotropic superstructures. The ordering within these arrays is also confirmed in bulk samples using small angle X‐ray scattering (SAXS).  相似文献   

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