Geometrical chirality is a property of objects that describes a three-dimensional mirror-symmetry violation and therefore it requires a nonvanishing spatial extent. In contrary, optical chirality describes only the local handedness of electromagnetic fields and neglects the spatial geometrical structure of optical beams. In this Letter we put forward the physical significance of geometrical chirality of spatial structure of optical beams, which we term Kelvin's chirality. Furthermore, we report on an experiment revealing the coupling of Kelvin's chirality to optical chirality upon transmission of a focused beam through a planar medium. Our work emphasizes the importance of Kelvin's chirality in all light-matter interaction experiments involving structured light beams with spatially inhomogeneous phase and polarization distributions.

中文翻译：

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开尔文光束的手性

几何手征性是对象的一种属性，它描述了三维镜像对称违规，因此它需要一个不变的空间范围。相反，光学手性仅描述电磁场的局部惯性，而忽略了光束的空间几何结构。在这封信中，我们提出了光束空间结构的几何手性的物理意义，我们称其为开尔文手性。此外，我们报告了一个实验，该实验揭示了聚焦光束通过平面介质传输时开尔文的手性与光学手性的耦合。我们的工作强调了开尔文手性在所有涉及具有空间上不均匀的相位和偏振分布的结构化光束的光-质相互作用实验中的重要性。