Spin–orbit photonic devices usually rely on 2D (transverse) material structuring and are designed for optimal coupling between the polarization state and the spatial degrees of freedom at a given wavelength. Exploiting the third dimension (longitudinal) provides ways to bypass monochromatic limitations. Within a singular optics framework, here we show that chiral liquid crystals endowed with non-singular 3D helix axis orientational distribution exhibit transmissive broadband spin–orbit optical vortex generation as well as an optical diode effect. These results are in stark contrast to the properties of spin–orbit optical elements fabricated from chiral liquid crystals with a uniform orientation of the helix axis, which are reflective devices that process forward and backward propagating waves equally. Moreover, the similarities between the proposed 3D chiral structure and that of the cuticle of some insects invites considering spin–orbit photonics from a biological perspective.

中文翻译：

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来自仿生 3D 手性液晶结构的自旋轨道光子二极管

自旋轨道光子器件通常依赖于二维（横向）材料结构，并且设计用于在给定波长下实现偏振态和空间自由度之间的最佳耦合。利用第三维（纵向）提供了绕过单色限制的方法。在奇异光学框架内，我们展示了具有非奇异 3D 螺旋轴取向分布的手性液晶表现出透射宽带自旋轨道光学涡旋产生以及光学二极管效应。这些结果与由螺旋轴方向一致的手性液晶制成的自旋轨道光学元件的特性形成鲜明对比，后者是一种反射装置，可以同等地处理前向和后向传播的波。而且，