Topological properties of light attract tremendous attention in the optics communities and beyond. For instance, light beams gain robustness against certain deformations when carrying topological features, enabling intriguing applications. We report on the observation of a topological structure contained in an optical beam, i.e., a twisted ribbon formed by the electric field vector per se, in stark contrast to recently reported studies dealing with topological structures based on the distribution of the time averaged polarization ellipse. Moreover, our ribbons are spinning in time at a frequency given by the optical frequency divided by the total angular momentum of the incoming beam. The number of full twists of the ribbon is equal to the orbital angular momentum of the longitudinal component of the employed light beam upon tight focusing, which is a direct consequence of spin-to-orbit coupling. We study this angular-momentum-transfer-assisted generation of the twisted ribbon structures theoretically and experimentally for tightly focused circularly polarized beams of different vorticity, paving the way to tailored topologically robust excitations of novel coherent light–matter states.

中文翻译：

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超快旋转受限电场的扭曲带

光的拓扑特性在光学界以及其他领域引起了极大的关注。例如，当光束具有拓扑特征时，它可以抵抗某些变形，因此具有很强的鲁棒性，可实现有趣的应用。我们报告观察到光束中包含的拓扑结构，即由电场矢量本身形成的扭曲带与最近报道的基于时间平均极化椭圆分布的拓扑结构研究形成鲜明对比。而且，我们的色带正在以光频率除以入射光束的总角动量所给定的频率随时间旋转。带的全扭曲数等于在紧密聚焦时所用光束的纵向分量的轨道角动量，这是自旋轨道耦合的直接结果。我们在理论上和实验上研究了具有不同涡度的紧密聚焦的圆偏振光束的扭曲带状结构的这种角动量传递辅助的产生，从而为新型相干光物质态的定制拓扑鲁棒激发铺平了道路。