Superscattering from Subwavelength Corrugated Cylinders

Abstract

Wave scattering from a cylinder with a tensor impedance surface is investigated based on the Lorentz-Mie theory. A practical example of such a cylinder is a subwavelength metallic rod with helical dielectric-filled corrugations. The investigation is performed with the aim to maximize scattering cross-section by tailoring the surface impedance of cylindrical scatterers. For the normally incident TEz and TMz waves the required surface impedance of a subwavelength cylinder can be produced by longitudinal (axial) and transverse (circumferential) corrugations, respectively. It is shown that such corrugations induce superscattering at multiple frequencies, which can be widely tuned with either or both the size and permittivity of dielectric-filled corrugations. In the microwave band, this effect is demonstrated to be robust to material losses and is validated against the fullwave simulations and experiment. For the TEz waves the enhanced scattering from the cylinder is found to have a broad frequency bandwidth, provided that the relative permittivity of corrugations is low or equal unity. In the latter case, the corrugated cylinder acts as an all-metal superscatterer. For such cylinders the near-field measurements are implemented and provide the first experimental evidence of the superscattering phenomenon for all-metal objects. In addition to multifrequency superscattering, the dielectric-filled corrugations are shown to provide multifrequency cloaking of the cylinder under the incidence of the TMz waves. Simultaneous superscattering and cloaking at multiple frequencies distinguishes corrugated cylinders from other known practicable scatterers for potential applications in antenna designing, sensing, and energy harvesting.Enhancement of wave scattering from small objects is a vital issue in present-day technologies [1-7], including miniaturized antennas, sensors and energy harvesting devices. This issue is directly related to the natural constraint inherent in most subwavelength scatterers [8]. This constraint is known as a single-channel limit [9], which represents an upper limit to scattering crosssection for such scatterers and is attained under resonance condition for one of the scattering modes (channels). The only way to overcome this constraint is to ensure resonant scattering of several modes at a single frequency. Such a resonance overlapping magnifies scattering from a given object and is known as superscattering [9,10]. The larger the number of resonant modes, the larger the superscattering cross-section. Therefore, theoretically, superscattering opens a way to arbitrary enhancement of wave scattering from subwavelength objects. In practice, however, this effect is often hindered by the lack of low-loss materials and appropriate design solutions.In the infrared and visible parts of spectrum, the superscattering can be realized in cylindrical structures formed by several plasmonic and dielectric layers. In the pioneering work [9], for such a structure the total scattering cross-section was optimized to excee...

Starting currents of modes in cylindrical cavities with mode-converting corrugations for second-harmonic gyrotrons

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Superscattering and Directive Antennas via Mode Superposition in Subwavelength Core-Shell Meta-Atoms

“…In many conventional structures, the fundamental natural resonances are separated in frequency and do not spectrally overlap significantly. In recent years however there has been a growing interest in the use of tailored systems where two or more resonant modes can be superimposed or 'stacked'-made to share a resonant frequency, leading to enhanced interaction with electromagnetic radiation and improved directivity in the farfield [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The combination of the lowest order (dipole) modes-a Huygens source, has been widely explored [3,4,[11][12][13][14][15], but the stacking of higher order modes has received less attention.…”

“…Mode stacking has enabled significant progress in controlling the power and directionality of radiation scattered by resonant particles when illuminated by a plane wave, which is key for technologies from light trapping in solar cells [17,18] to radar detection [19]. The spectral overlap of two or more modes in a variety of geometries has produced powerful scattering, that surpasses the theoretical single channel limit [20] in both the microwave [1,2,15] and optical regimes [14,21] as well as producing directional emission and suppressed backscatter. The opposite case, where backscattered power is maximized, has also been posited theoretically by Liberal et al [22] and Nagarhi et al [23] who demonstrated that overlapping modes with equivalent phase of radiation in the reverse direction leads to a maximization of backscattered power, which has been recently experimentally verified by the authors [16].…”

Manipulating Optical Scattering of Quasi-BIC in Dielectric Metasurface with Off-Center Hole

“…Scattering manipulation lays the foundation of modern photonics, which has outstanding prospects in wavefront manipulation, optical signal processing, energy collection, and sensing. In recent years, one of the main focuses in nanophotonics is to manipulate the optical scattering in order to obtain novel properties unavailable for traditional optical materials and structures [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”