Theory, Observation, and Ultrafast Response of the Hybrid Anapole Regime in Light Scattering
Theory, Observation, and Ultrafast Response of the Hybrid Anapole Regime in Light Scattering
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DOI：
10.1002/lpor.202100114
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发表时间：
2021-08
影响因子：
11
通讯作者：
A. Canós Valero;E. Gurvitz;F. Benimetskiy;D. Pidgayko;A. Samusev;A. Evlyukhin;V. Bobrovs;Dmitrii Redka;M. Tribelsky;M. Rahmani;K. Z. Kamali;A. Pavlov;A. Miroshnichenko;A. Shalin
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作者：
A. Canós Valero;E. Gurvitz;F. Benimetskiy;D. Pidgayko;A. Samusev;A. Evlyukhin;V. Bobrovs;Dmitrii Redka;M. Tribelsky;M. Rahmani;K. Z. Kamali;A. Pavlov;A. Miroshnichenko;A. Shalin
现代纳米光子学见证了“电偶极子”(EDAS)的兴起，它是电偶极子和环形电偶极子的破坏性干扰，被积极利用来共振地减少来自纳米谐振器的辐射。然而，麦克斯韦方程中固有的对偶性暗示了“磁极”有趣的可能性，它包括一个磁偶极子和一个磁环偶极子的非辐射组合。在这里，我们通过暗场光谱预测和实验观测到了一种具有混合电磁特性的混合极点(HA)，其中所有占主导地位的多极都被纳米柱体中的环向项所抑制。打破球对称，只需两个调谐参数，就可以重叠最多四个来自不同多极的极点。这种效应是由于谐振器多极响应及其本征态之间的对称性连接造成的。作者深入研究了稳态和瞬变区域中这种电流组态的物理学，并探索了与HA动力学相关的在亚皮秒时间尺度上出现的新的超快现象。理论结果允许设计具有双重功能的非惠更斯亚表面：在稳态区完全透明，在瞬变区可控的超短脉冲跳动。除了提供与EDAS相比的显著优势外，HAS还可以在开发新兴的超快共振现象领域发挥重要作用。
Modern nanophotonics has witnessed the rise of “electric anapoles” (EDAs), destructive interferences of electric and toroidal electric dipoles, actively exploited to resonantly decrease radiation from nanoresonators. However, the inherent duality in Maxwell equations suggests the intriguing possibility of “magnetic anapoles,” involving a nonradiating composition of a magnetic dipole and a magnetic toroidal dipole. Here, a hybrid anapole (HA) of mixed electric and magnetic character is predicted and observed experimentally via dark field spectroscopy, with all the dominant multipoles being suppressed by the toroidal terms in a nanocylinder. Breaking the spherical symmetry allows to overlap up to four anapoles stemming from different multipoles with just two tuning parameters. This effect is due to a symmetry‐allowed connection between the resonator multipolar response and its eigenstates. The authors delve into the physics of such current configurations in the stationary and transient regimes and explore new ultrafast phenomena arising at sub‐picosecond timescales, associated with the HA dynamics. The theoretical results allow the design of non‐Huygens metasurfaces featuring a dual functionality: perfect transparency in the stationary regime and controllable ultrashort pulse beatings in the transient. Besides offering significant advantages with respect to EDAs, HAs can play an essential role in developing the emerging field of ultrafast resonant phenomena.