Orientational Photorefractive Effect in Undoped and CdSe Nanorods-Doped Nematic Liquid Crystal—Bulk and Interface Contributions
Orientational Photorefractive Effect in Undoped and CdSe Nanorods-Doped Nematic Liquid Crystal—Bulk and Interface Contributions
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DOI：
10.1109/jstqe.2006.871955
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发表时间：
2006-06
影响因子：
4.9
通讯作者：
I. Khoo;K. Chen;Y. Williams
中科院分区：
文献类型：
--
作者：
I. Khoo;K. Chen;Y. Williams
在工作中，我们重新研究了向列液晶（NLC）在简并四波混合相互作用构型下产生的取向光折变效应。得到了块体激光诱导的空间电荷场的详细计算公式，以及重定向角和所需直流阈值场的解析表达式，并与实验测量结果进行了比较。虽然体理论可以描述自衍射场和阈值场的一般特征，但与实验观察有很大的偏差，特别是在观察到的阈值电压随光强的降低。这种效应是由于光学诱导的表面电荷调制。包括体和表面电荷调制效应的理论分析使我们能够与实验观察到的阈值电压对光强度和样品厚度的影响有更好的一致性，并估计了体和表面效应的相对贡献。最近观察到的CdSe纳米棒掺杂NLCs的增强光折变效应也被报道，以证实这些分析，并为优化动态全息应用的光折变效应提供指导。
In the work, we revisited the orientational photorefractive effect generated in nematic liquid crystal (NLC) in a degenerate four-wave mixing interaction configuration. A detailed calculation of the bulk laser-induced space-charge fields and analytical expressions for the reorientation angles and the required dc threshold fields are obtained and compared with experimental measurements. While the bulk theory could describe the general features of the self-diffraction and threshold fields, there are significant deviations from experimental observation, particularly in an observed lowering of the threshold voltage by the optical intensity. This effect is due to an optically induced surface-charge modulation. A theoretical analysis including both the bulk and the surface-charge-modulation effects allows us to obtain better agreement with experimental observations of the threshold voltages on the optical intensity and sample thicknesses, and to estimate the relative contributions from the bulk and surface effects. Recently observed enhanced photorefractive effects of CdSe nanorods-doped NLCs are also reported to corroborate these analyses and to provide guidelines to optimize the photorefractive effect for dynamic holographic application.