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首页> 外文会议>International Conference on Nonlinear Optics of Liquid and Photorefractive Crystals >Variations of the helix in thin planar cholesteric layers influenced by surface anchoring
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Variations of the helix in thin planar cholesteric layers influenced by surface anchoring

机译：薄平面胆甾型层中螺旋的变化受表面锚固影响

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Unwinding (winding) of a helix in thin planar cholesteric layers induced by the varying external parameters (temperature, electric or magnetic field) and its dependence on the surface anchoring are theoretically investigated for the defectless mechanism of the cholesteric pitch jumps connected with a slipping of the director on the surface through the anchoring potential barrier. Earlier investigations of the problem performed for the case of the temperature variations showed strong dependence of the relevant phenomena on the anchoring potential (two sets of model anchoring potentials were considered). However the field dependence of the pitch variations was examined only for the Rapini-Papoular (R-P) anchoring potential. We performed investigation of the problem for two types anchoring potentials, R-P - potential and so called B-potential and found a qualitatively different behavior of the pitch in applied field for the different types of potential. The parameter Sd = K22/(dW) (where K22 is the twist constant, W is the height of the anchoring potential and d is the sample thickness) governs the "pitch versus applied field (temperature)" dependence. The field dependences of the pitch are calculated for a planar cholesteric layer with infinite strength of anchoring at one surface and finite strength of anchoring at the second one for the R-P and B-surface anchoring potentials. It is found that for the B-potential the pitch jumps and hysteresis of these jumps exists at any strength of anchoring opposite to the case of the R-P-potential for which the jumps and hysteresis exist for sufficiently strong anchoring only when Sd<1. In particular it is shown that the critical field of the complete helix unwinding Ec, in a thin layer may be as essentially lower than the critical field in a bulk cholesteric so larger than this field and for some range of the relevant to the problem parameters the helix unwounded by the field remains to be unwounded after removing of the field.
机译：由不同的外部参数（温度，电动场）引起的薄平面胆甾型层的螺旋中的螺旋（绕组）在理论上研究了与滑动连接的胆甾型间距跳跃的缺陷机构的理论上研究通过锚定电位屏障在表面上的导演。早期对对温度变化的情况执行的问题的研究表明，对锚定电位的相关现象的强烈依赖性（考虑了两组模型锚定电位）。然而，仅针对Rapini-PapOular（R-P）锚固潜力检查间距变化的场依赖性。我们对两种类型的锚固电位，R-P - 电位和所谓的B潜力进行了研究的研究，并发现了用于不同类型的潜力的施加场中的音调的定性不同的行为。参数SD = K22 /（DW）（其中，K22是恒定的扭曲，W是所述锚定电位的高度，d是样品厚度）支配“节距与施加的场（温度）”的依赖。间距的场依赖性针对平面胆甾型层计算，其具有锚固在一个表面上的无限强度和用于R-P和B表面锚固电位的第二锚固的有限强度。据发现，对于B-电位间距跳跃和这些跳跃滞后的锚固相反的R-P-电位的量，跳转和滞后存在的情况下为足够强的锚定只有当Sd中<1的任何强度存在。特别地，示出了完整的螺旋退绕的Ec，以薄层的临界场可以是本质上比在散装胆甾所以比该领域较大临界场并且对于一些范围相关的对问题的参数降低螺旋未受损由现场遗体领域进行去除后进行未受伤。

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