Directional Toroidal Dipoles Driven by Oblique Poloidal and Loop Current Flows in Plasmonic Meta-Atoms
Directional Toroidal Dipoles Driven by Oblique Poloidal and Loop Current Flows in Plasmonic Meta-Atoms
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DOI：
10.1021/acs.jpcc.8b08184
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发表时间：
2018-10-25
影响因子：
3.7
通讯作者：
Gerislioglu, Burak
中科院分区：
文献类型：
--
作者：
Ahmadivand, Arash;Gerislioglu, Burak
环形偶极子是一种精致而非传统的电磁模式，它与众所周知的传统多极子群是分开的，后者可以在一个极其微小的光点上强健地局域化和压缩。在光学亚波长系统中，这种动态模式以头尾相连的方式表现出来，这种模式可以特别地区分为无辐射的电荷-电流配置。在这里，我们超越了传统的环形偶极子，解释了通过控制斜磁场和极向磁通来驱动等离子体准原子激发定向环形偶极子的可能性。这是通过利用在近红外波段具有强环向响应的反对称多像素单元来实现的。我们发现，这种非对称纳米结构的独特结构性质导致了多个方向的环形模式的形成，这些模式具有相反的斜磁场和反向的极向电流。我们预计，这一理解将为多共振环形准原子的实际应用铺平新的道路，用于从调制到光束控制的高级纳米光子学应用。
The toroidal dipole is an exquisite and untraditional electromagnetic mode, categorizing separately from the well-known conventional multipole group which can be robustly localized and squeezed in an extremely tiny spot. In optical subwavelength systems, such a dynamic mode, which can be particularly distinguished as a nonradiating charge-current configuration, manifests in a head-to-tail fashion. Here, going beyond conventional toroidal dipoles, we explained the possibility of the excitation of directional toroidal dipoles in plasmonic meta-atoms driven by controlling the oblique magnetic field and poloidal fluxes. This was done by utilizing an antisymmetric multipixel unit cell with strong toroidal response across the near-infrared band. We showed that the unique structural properties of the proposed asymmetric nanostructure lead to the formation of multiple directional toroidal modes with opposite oblique magnetic fields and reverse poloidal current flows. We envision that this understanding paves novel approaches for the practical purposes of the multiresonant toroidal meta-atoms for advanced nanophotonic applications from modulation to beam steering.