Abstract Magneto-optical materials have become a key tool in functional nanophotonics, mainly due to their ability to offer active tuning between two different operational states in subwavelength structures. In the long-wavelength limit, such states may be considered as the directional forward- and back-scattering operations, due to the interplay between magnetic and electric dipolar modes, which act as equivalent Huygens sources. In this work, on the basis of full-wave electrodynamic calculations based on a rigorous volume integral equation (VIE) method, we demonstrate the feasibility of obtaining magnetically-tunable directionality inversion in spherical microresonators (THz antennas) coated by magneto-optical materials. In particular, our analysis reveals that when a high-index dielectric is coated with a magneto-optical material, we can switch the back-scattering of the whole particle to forward-scattering simply by turning off/on an external magnetic field bias. The validity of our calculations is confirmed by reproducing the above two-state operation, predicted by the VIE, with full-wave finite-element commercial software. Our results are of interest for the design of state-of-the-art active metasurfaces and metalenses, as well as for functional nanophotonic structures, and scattering and nanoantennas engineering.

中文翻译：

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球形微谐振器中克尔克散射的磁开关

摘要 磁光材料已成为功能纳米光子学的关键工具，主要是因为它们能够在亚波长结构的两种不同操作状态之间提供主动调谐。在长波长极限下，由于磁偶极模式和电偶极模式之间的相互作用，这种状态可以被认为是定向前向和反向散射操作，它们充当等效的惠更斯源。在这项工作中，在基于严格体积积分方程 (VIE) 方法的全波电动力学计算的基础上，我们证明了在由磁光材料涂覆的球形微谐振器 (THz 天线) 中获得磁可调方向性反转的可行性。特别是，我们的分析表明，当高指数电介质涂有磁光材料时，我们可以通过关闭/打开外部磁场偏置，将整个粒子的反向散射切换为正向散射。通过使用全波有限元商业软件重现由 VIE 预测的上述两种状态操作，我们的计算的有效性得到了证实。我们的结果对设计最先进的有源超表面和超透镜，以及功能性纳米光子结构以及散射和纳米天线工程具有重要意义。