Surpassing super-radiant scattering limit in a flat split-ring resonator
Abstract
Electromagnetic scattering bounds on subwavelength structures play an important role in estimating performances of antennas, RFID tags, and other wireless communication devices. An appealing approach to increase a scattering cross-section is accommodating several spectrally overlapping resonances within a structure. However, numerous fundamental and practical restrictions have been found and led to the formulation of Chu-Harrington, Geyi, and other limits, which provide an upper bound to scattering efficiencies. Here we introduce a 2D array of near-field coupled split-ring resonators and optimize its scattering performances with the aid of a genetic algorithm, operating in 19th-dimensional space. Experimental realization of the device is demonstrated to surpass the theoretical single-channel limit by a factor of >2, motivating the development of tighter bounds of scattering performances. A super-radiant criterion is suggested to compare maximal scattering cross-sections versus the single-channel dipolar limit multiplied by the number of elements within the array. This new empirical criterion, which aims on addressing performances of subwavelength arrays formed by near-field coupled elements, was found to be rather accurate in application to the superscatterer, reported here. Furthermore, the super-radiant bound was empirically verified with a Monte-Carlo simulation, collecting statistics on scattering cross sections of a large set of randomly distributed dipoles. The demonstrated flat superscatterer can find use as a passive electromagnetic beacon, making miniature airborne and terrestrial targets to be radar visible.
Cite
@article{arxiv.2209.12627,
title = {Surpassing super-radiant scattering limit in a flat split-ring resonator},
author = {Anna Mikhailovskaya and Konstantin Grotov and Dmytro Vovchuk and Andrey Machnev and Dmitry Dobrykh and Roman E. Noskov and Konstantin Ladutenko and Pavel Belov and Pavel Ginzburg},
journal= {arXiv preprint arXiv:2209.12627},
year = {2022}
}
Comments
20 pages, 6 figures