In practically all branches of physics, different types of solitons, with a number of them enjoying topological protection, are found. Here we explore how one- and two-dimensional topological solitons formed by spatially localized continuous orientational patterns of optical axis in uniaxial birefringent media interact with light. These solitons, in the forms of one-dimensional twist walls and two-dimensional skyrmions, are controllably generated in thin films of cholesteric liquid crystals to introduce spatially localized patterns of effective refractive index. Laser light interacts with these solitons as quasiparticles or extended interfaces of different effective refractive indices seen by ordinary and extraordinary waves propagating within the liquid-crystal medium. Despite our system’s complex nature, our findings can be paralleled with the familiar phenomena of total reflection and refraction at interfaces of optically distinct media, albeit these behaviors arise in a medium with homogeneous density and chemical composition but with spatial variations of molecular and optical-axis orientations. By exploiting the facile response of liquid crystals to external stimuli, we show that the twist walls and skyrmions can be used to steer laser beams and to act as lenses and other optical elements, which can be reconfigured by low-voltage fields and other means. Analytical and numerical modeling, with the latter based on free-energy-minimizing configurations of the topological solitons, closely reproduce our experimental findings. The fundamental insights provided by this work potentially can be extended also to three-dimensional solitons, such as Hopfions, and may lead to technological applications of optical-axis topological solitons in telecommunications, nanophotonics, electro-optics, and so on.

中文翻译：

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软手性双折射介质中拓扑孤子对光的控制

在几乎所有的物理学分支中，都发现了不同类型的孤子，其中许多孤子都具有拓扑保护。在这里，我们探索由单轴双折射介质中的光轴在空间上定位的连续定向图案形成的一维和二维拓扑孤子如何与光相互作用。这些孤子以一维扭曲壁和二维天生离子的形式可控地在胆甾型液晶薄膜中生成，以引入有效折射率的空间局部分布图。激光与这些孤子相互作用，成为准粒子或不同有效折射率的扩展界面，这种现象可以在液晶介质中传播的寻常波和异常波看到。尽管我们的系统性质复杂，我们的发现可以与光学不同介质界面处的全反射和折射现象相熟悉，尽管这些行为出现在密度和化学成分均一但分子和光轴方向具有空间变化的介质中。通过利用液晶对外部刺激的轻松响应，我们显示出扭曲壁和天体可以用来操纵激光束，并可以用作透镜和其他光学元件，可以通过低压场和其他方式对其进行重新配置。解析和数值建模，其中后者基于拓扑孤子的自由能最小化配置，紧密地再现了我们的实验结果。这项工作提供的基本见解还可以扩展到三维孤子，