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Photonics 2019, 6(2), 43;

The Observation of High-Order Charge–Current Configurations in Plasmonic Meta-Atoms: A Numerical Approach

Department of Physics and Astronomy, Rice University, 6100 Main St, Houston, TX 77005, USA
Author to whom correspondence should be addressed.
Received: 19 March 2019 / Revised: 11 April 2019 / Accepted: 15 April 2019 / Published: 16 April 2019
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Living in a world of resonances, there have been significant progresses in the field of excitation of pronounced and multifunctional moments across a wide range of optical frequencies. Among all acknowledged resonances, the toroidal multipoles have received copious interest in recent years due to possessing inherent signatures in nature. As a fundamental member, toroidal dipole is a strongly localized electromagnetic excitation based on charge–current configurations, which can be squeezed into an extremely small spot. Although there have been extensive studies on the behavior and properties of toroidal dipoles in order to develop all-optical devices based on this technology, so far, all analyses are restricted to the first (1st) order toroidal dipoles. In this work, using a practical technique, we successfully observed exquisite multi-loop super-toroidal (MLST) spectral features in a planar multipixel metallodielectric meta-atom. Employing the theory behind the excitation of multi-loop currents, we numerically and theoretically demonstrated that a traditional toroidal dipole can be transformed into a super-toroidal moment by varying the dielectric permittivity of the capacitive gaps between proximal pixels. This understanding introduces a new approach for the excitation of complex multi-loop toroidal moments in plasmonic metamaterials with high sensitivity, applicable for various nanophotonics applications from sensing to filtering. View Full-Text
Keywords: toroidal dipole; plasmonic meta-atoms; multi-loop currents; super-toroidal moment toroidal dipole; plasmonic meta-atoms; multi-loop currents; super-toroidal moment

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Gerislioglu, B.; Ahmadivand, A. The Observation of High-Order Charge–Current Configurations in Plasmonic Meta-Atoms: A Numerical Approach. Photonics 2019, 6, 43.

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