Volume-stabilized ULH structure for the flexoelectro-optic effect and the phase-shift effect in cholesterics
Volume-stabilized ULH structure for the flexoelectro-optic effect and the phase-shift effect in cholesterics
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DOI：
10.1080/026782998207127
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发表时间：
1998-03-01
期刊：
影响因子：
2.2
通讯作者：
Lagerwall, ST
中科院分区：
文献类型：
--
作者：
Rudquist, P;Komitov, L;Lagerwall, ST
柔性电耦合在具有均匀排列螺旋(ULH)结构的胆甾体中产生线性电光响应(挠曲电光效应)，这种电光效应强烈依赖于织构的均匀性和质量。不幸的是，ULH结构本身是复杂的，可能会受到介电耦合、表面/液晶相互作用和相变等因素的干扰，并且随着时间的推移往往有松弛为格兰杰织构(站立螺旋结构)的趋势。因此，为了利用胆甾体中的挠曲电光效应，必须排除ULH结构的任何不稳定性。我们通过在胆甾体中加入反应性单体的光聚合来结合聚合物网络来克服这些问题。体积稳定的ULH结构仍然表现出挠曲电光效应，它是稳定的，加热到各向同性相并返回胆甾相后仍保持不变。除了挠曲电光模式之外，ULH结构还涉及电光模式，其特征是在幅度(透过率)不变的情况下具有纯相移。并简要讨论了该模式在空间光调制器、光计算器件以及无偏振器工作的电控相图和位相全息图中的明显应用。
Flexoelectric coupling gives rise to a linear electro-optic response in cholesterics (flexoelectro-optic effect) with a uniformly lying helix (ULH) structure and this electro-optic effect is strongly reliant on the homogeneity and quality of the texture. The ULH structure, unfortunately, is complicated in itself and may be perturbed by factors such as dielectric coupling, surface/liquid crystal interactions and phase transitions, and often there is a tendency for relaxation into the Grandjean texture (standing helix structure) with time. Hence, in order to exploit the flexoelectro-optic effect in cholesterics any instability of the ULH structure must be ruled out.We have overcome these problems by incorporating a polymer network by means of photopolymerization of a reactive monomer added to the cholesteric. The volume stabilized ULH structure still exhibits the flexoelectro-optic effect, it is stable and it is also retained after heating to the isotropic phase and going back to the cholesteric phase. In addition to the flexoelectro-optic mode, the ULH structure is of interest in an electro-optic mode characterized by a pure phase-shift with no change in amplitude (transmittance). This mode, which has obvious applications in spatial light modulators, optical computing devices and electrically controlled kinoforms and phase holograms working without polarizers, is also briefly discussed.