|0⟩ |1⟩ |2⟩ 4 J J J J P P 5 C J C P C U L Figure 1: Topolectrical circuit model. a, Artistic view of two-photon excitations in the array of microresonators with tunneling couplings. The depicted state isâ † 1â † 3 |0 . b, Extended version of Bose-Hubbard model considered in the present article. Single-photon tunnelings J are shown by blue solid lines, direct two-photon tunnelings P are indicated by purple wavy lines. c, Top view of the equivalent two-dimensional topolectrical circuit with a voltage at the site (m, n) corresponding to probability amplitude βmn for one photon to be located at the m th resonator of the array with another one located at the n th resonator [cf. Eq. (2)]. Colored regions show characteristic voltage patterns for two-photon scattering states (green), doublons (red), and doublon edge state (blue). External voltage source applied for the system excitation and voltmeter are shown to the right. Side view of the diagonal (lower inset) and off-diagonal (upper inset) sites of the topolectrical circuit, where grounding elements are shown. d, The photograph of experimental setup having the size of 15 × 15 nodes. Inset shows the enlarged fragment of the circuit which includes two unit cells. d c b a J J P J P J J P J
one of the most exciting applications of metaparticles and metasurfaces consists in the magnetic light excitation. However, the principal limitation is due to parasitic extra multipoles of electric family excited in magnetic dipole meta-particles characterized by a radiating nature and corresponding radiating losses. in this paper, we propose the "ideal magnetic dipole" with suppressed additional multipoles except of magnetic dipole moment in the scattered field from a cylindrical object by using mantle cloaking based on metasurface and on anapole concept. the considered metasurface consists of a periodic width modulated microstrip line, with a sinusoidally shaped profile unit cell printed on a dielectric substrate.Despite of the progress in electromagnetics, the light-matter interaction is still associated especially with electric component of light, while magnetic component is suppressed down to negligible level, particularly at more anticipated optical frequencies. On the other hand, magnetic light-matter interaction is promising playground for unusual effects like negative refraction 1-4 , magnetoinductive waves 5 , fluorescent microscopy 6,7 , nanoscale imaging and others 8,9 . Therefore, magnetic response of subwavelength particles contributes to optical magnetism leading to effects such as magnetic light 10 , magnetic nanoantennas 11-15 and magnetic Purcell effect [16][17][18][19] . For this sake, recent works propose various techniques for artificial magnetism that enable strong magnetic field localization even for nonferromagnetic particles that is usually several times weaker than the electric field component counterpart [20][21][22][23][24] . The first realization of artificial magnetic dipole (MD) has been demonstrated in metal split-ring resonator (SRR), thereafter becoming a basic element of metamaterials 3,25,26 . Overall, strongly concentrated magnetic field can be excited by a circular current oscillating within the SRR and mimicking a MD. The idea of SRR is still of high demand; however, its application is restricted by the impossibility of implementation in visible frequency range due to intrinsic metallic particles with high Joule losses 26 . A second limitation is due to the excitation of parasitic extra multipoles of electric family characterized by a radiating nature and corresponding radiating losses. Thus, researchers are approaching to achieve an ideal magnetic dipole without additional multipoles (except of magnetic dipole moment) in the system.The idea of the ideal MD scatterer can be elegantly described by multipole decomposition theory of the scattering from resonant particles. This approach allows studying the radiation properties by description of the scattering cross-section as a sum of electric a E (l, m) and magnetic a M (l, m) scattering coefficients. Indeed, the resulting scattering efficiency Q sca is given by the superposition of electric and magnetic scattered multipoles:where l is the number of spherical harmonics defining multipoles order. In this way, we can calculate th...
In this paper, an analysis of the spectral composition of the scattered field from coated metallic cylinders is performed, focusing particularly on the cloaking of electrically large structures. An expression of the scattering coefficients is derived, considering both a dielectric and a metasurface coating. Modeling the metasurface as a surface impedance boundary condition, the surface impedance, which annuls one harmonic of the scattered field, is formulated in a closed and compact form. Moreover, in the case of cylinders with radius comparable with the wavelength of interest, it is demonstrated that a reduction of the scattering is possible by using a homogeneous metasurface coating, which presents a positive surface reactance. In particular, a reduction of the scattering width of 4 dB is achieved for a cylinder radius of a = 0.917 λ 0 .
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