ABSTRACT The field-induced orientational transition in layers of cholesteric liquid crystals with spatially periodic modulation of the surface anchoring is studied by numerical simulations and experimentally. The modulation of the surface anchoring is implemented using high-resolution focused ion-beam treatment of a polymer film providing planar alignment conditions. A specific feature of the orientational transition is that the thermodynamically stable initial planar structure with the helix axis along the normal to the layer transforms under an electric field into an equilibrium structure with a deformed lying helix (DLH) in the plane of the layer. For such a transition to occur the natural pitch of the cholesteric helix must be substantially less than the anchoring modulation period. The appearance of the DLH with a pitch corresponding to the anchoring modulation period results in strongly enhanced first-order diffraction efficiency. The orientational DLH transition is characterised by a rather narrow driving voltage range with a pronounced hysteresis. The waveguide lasing effect with characteristic of the deformed helix spectral modes is demonstrated in a range of the DLH transition. GRAPHICAL ABSTRACT

中文翻译：

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空间周期边界条件下胆甾型液晶层中的变形螺旋跃迁和激光效应

摘要 通过数值模拟和实验研究了具有表面锚定空间周期性调制的胆甾型液晶层中场诱导的取向转变。表面锚定的调制是使用聚合物膜的高分辨率聚焦离子束处理实现的，提供平面对准条件。取向转变的一个具体特征是具有沿层法线的螺旋轴的热力学稳定的初始平面结构在电场作用下转变为在层平面中具有变形的螺旋(DLH)的平衡结构。为了发生这种转变，胆甾型螺旋的自然螺距必须显着小于锚定调制周期。具有对应于锚定调制周期的节距的 DLH 的出现导致一阶衍射效率的强烈增强。定向 DLH 转变的特点是驱动电压范围相当窄，具有明显的滞后。具有变形螺旋光谱模式特征的波导激光效应在 DLH 跃迁范围内得到证明。图形概要