On the Existence of Pure, Broadband Toroidal Sources in Electrodynamics
Laser and Photonics Reviews 2024
Andria Canos Valero, Dmitrii Borovkov, Aleksandr Kalganov, Alexandra Dudnikova, Mikhail Sodorenko, Pavel Dergachev, Egor Gurvitz, Lei Gao, Vjačeslavs Bobrovs, Andrey Miroshnichenko, Aleksandr Shalin

Multipoles are paramount for describing electromagnetic fields in many areas of nanoscale optics, playing an essential role in the design of devices in plasmonics and all-dielectric nanophotonics. Challenging the traditional division into electric and magnetic moments, toroidal moments are proposed as a physically distinct family of multipoles with significant contributions to the properties of matter. However, the apparent impossibility of separately measuring their response sheds doubt on their true physical significance. Here, the possibility of selectively exciting toroidal moments is confirmed without any other multipole. A set of general conditions is developed that any current distribution must fulfill to be entirely described by toroidal moments and prove the results in an analytically solvable case. The new theory allows to design and verify experimentally an artificial structure supporting a pure broadband toroidal dipole response in the complete absence of the electric dipole and other “ordinary” multipole contributions. In addition, a structure capable of supporting a novel type of non-radiating source is proposed- a “toroidal anapole,” originating from the destructive interference of the toroidal dipole with the unconventional electromagnetic sources known as mean square radii. The results in this work provide conclusive evidence on the independent excitation of toroidal moments in electrodynamics. © 2024 The Authors. Laser & Photonics Reviews published by Wiley-VCH GmbH.

Atslēgas vārdi
all-dielectric nanophotonics; anapole; multipoles; toroidal dipole; toroidal moments

Canos Valero, A., Borovkov, D., Kalganov, A., Dudnikova, A., Sodorenko, M., Dergachev, P., Gurvitz, E., Gao, L., Bobrovs, V., Miroshnichenko, A., Shalin, A. On the Existence of Pure, Broadband Toroidal Sources in Electrodynamics. Laser and Photonics Reviews, 2024, Vol. 18, 1.-11.lpp. ISSN 1863-8880. e-ISSN 1863-8899. Pieejams: doi:10.1002/lpor.202200740

Publikācijas valoda
English (en)
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