Besides the fundamental Mie resonance modes of high‐index dielectric nanostructures, an extended multipole family, i.e., toroidal multipoles, provide great opportunities for engineering a new class of nanophotonic devices. Here, it is demonstrated theoretically and experimentally that a hexagonal array of circular silicon (Si) nanodisks (NDs) supports intra‐ and inter‐ND toroidal dipole (TD) modes. The key concept is the alignment of Si NDs near the anapole state condition for constructive interaction of the TD modes between neighboring NDs. Numerical simulation reveals that strong field confinement by the coupled TD modes enhances the absorption 120‐fold at the resonance wavelength compared to that of a flat Si film with the same thickness. In this study, macroscopic scale hexagonal Si ND arrays are fabricated using a colloidal lithography, and spectrally selective absorption enhancement due to the TD modes is demonstrated. Furthermore, it is demonstrated that a dipolar emitter can also excite TD modes, which modify the spectral shape and the directionality of the emission.

中文翻译：

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硅纳米盘超表面上的耦合环形偶极子模式：极化独立的窄带吸收和定向发射。

除了高折射率介电纳米结构的基本Mie共振模式外，扩展的多极子族（即环形多极子）为设计新型纳米光子器件提供了巨大的机会。在此，从理论上和实验上证明，圆形硅（Si）纳米磁盘（NDs）的六边形阵列支持ND内和ND环形偶极子（TD）模式。关键概念是在偶极状态条件附近对准Si ND，以便相邻ND之间TD模式的建设性相互作用。数值模拟表明，与相同厚度的平坦Si膜相比，耦合TD模式对强电场的限制使共振波长处的吸收提高了120倍。在这项研究中，使用胶体光刻技术制作了宏观尺度的六角形Si ND阵列，并证明了由于TD模式引起的光谱选择性吸收增强。此外，已经证明，偶极发射极也可以激发TD模式，从而改变发射的光谱形状和方向性。