Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch
Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch
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DOI：
10.1002/adom.201500159
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发表时间：
2015-09-01
影响因子：
9
通讯作者：
Shibaev, Valery
中科院分区：
文献类型：
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作者：
Ryabchun, Alexander;Bobrovsky, Alexey;Shibaev, Valery
阐述了一种基于螺距可调的胆甾型液晶的新型可旋转衍射体光栅。为此，我们开发了含有偶氮苯衍生物的手性光致变色掺杂剂，具有高螺距可调性和可逆光致螺旋利手反转的胆甾型液晶混合物。结果表明，在混合(同向同性-平面)边界条件下制备的胆甾相混合物自发地形成了取向良好的条状磁畴织构，起到了位相光栅的作用。在光的作用下，由于手性光致变色掺杂剂的分子光反应引起螺旋螺距的变化，导致了条形磁区结构的周期及其旋转的变化。相应地，通过在紫外光和可见光之间切换，可以实现所获得的光栅的顺时针和逆时针旋转。连续旋转的最大角度约为690度，而紫外光照明引起的总旋转约为1220度。演示了通过胆碱相区域织构的局部光曝光来创建各种复杂组织结构。从科学和应用的角度来看，观测到的先进的光学效应具有潜在的广泛和重要的应用前景。
A novel type of rotatable diffraction volume gratings based on cholesteric liquid crystals with phototunable helix pitch is elaborated. For this purpose the cholesteric liquid crystalline mixture with high helix pitch tunability and reversible photoinduced helix handedness inversion containing azobenzene-derivative of the chiral-photochromic dopant is developed. It was shown that the prepared cholesteric mixture under the hybrid (homeotropic - planar) boundary conditions spontaneously forms a well-oriented striped domain texture which acts as a phase grating. Under the effect of light the changes of helix pitch take place due to the molecular photoreaction of chiral-photochromic dopant causing the variation of the period of striped domain structure and its rotation. The clockwise and counterclockwise rotation of the obtained gratings can be achieved by switching between UV and visible light, correspondingly. The maximum angle of the continuous rotation is approximate to 690 degrees, while the total rotation caused by UV light illumination reaches approximate to 1220 degrees. The creation of a variety of complex-organized structures by local light exposure of the cholesteric domain texture is demonstrated. The observed advanced photooptical effects have potentially wide and important applications from scientific and applied points of view.