Transient Reorientation of a Doped Liquid Crystal System under a Short Laser Pulse
Transient Reorientation of a Doped Liquid Crystal System under a Short Laser Pulse
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DOI：
10.1088/0256-307x/26/8/086108
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发表时间：
2009-07
影响因子：
3.5
通讯作者：
Li Tao;X. Ying;Liu Yikun;Wang Jian;Yang Shun-Lin
中科院分区：
文献类型：
--
作者：
Li Tao;X. Ying;Liu Yikun;Wang Jian;Yang Shun-Lin
本文研究了偶氮染料DR_（19）掺杂双折射液晶的瞬态光学非线性。在25 μ m厚的5CB平面取向样品中，加入1vol%的偶氮掺杂剂后，用532 nm YAG激光脉冲（脉宽50 ns），观察到光学重取向阈值从800 mJ/mm（2）下降到0.6mJ/mm（2），下降了三个数量级。当使用10 ns的激光脉冲持续时间时，没有观察到这种效应。实验结果表明，在光照条件下，偶氮掺杂剂分子发生了由反式异构体向顺式异构体的光致异构化，这种构象变化通过主客体之间的分子间耦合使5CB分子重新取向.这种客体-主体耦合也影响偶氮光异构化过程。
The transient optical nonlinearity of a nematic liquid crystal doped with azo-dye DR19 is examined. The optical reorientation threshold of a 25-mu m-thick planar-aligned sample of 5CB using a 50 ns pulse duration 532 nm YAG laser pulse is observed to decrease from 800 mJ/mm(2) to 0.6 mJ/mm(2) after the addition of 1 vol% azo dopant, a reduction of three orders of magnitude. When using a laser pulse duration of 10 ns, no such effect is observed. Experimental results indicate that the azo dopant molecules undergo photoisomerization from trans-isomer to cis-isomer under exposure to light, and this conformation change reorients the 5CB molecules via intermolecular coupling between guest and host. This guest-host coupling also affects the azo photoisomerization process.