Gyromagnetically Induced Transparency of Metasurfaces

Abstract

We demonstrate that the presence of a (gyro)magnetic substrate can produce an analog of electromagnetically induced transparency in Fano-resonant meta-molecules. The simplest implementation of such gyromagnetically induced transparency (GIT) in a meta-surface, comprised of an array of resonant antenna pairs placed on a gyromagnetic substrate and illuminated by a normally incident electromagnetic wave, is analyzed. Time reversal and spatial inversion symmetry breaking introduced by the DC magnetization makes meta-molecules bi-anisotropic. This causes Fano interference between the otherwise uncoupled symmetric and anti-symmetric resonances of the meta-molecules giving rise to a sharp transmission peak through the otherwise reflective meta-surface. We show that, for an oblique wave incidence, one-way GIT can be achieved by the combination of spatial dispersion and gyromagnetic effect. These theoretically predicted phenomena pave the way to nonreciprocal switches and isolators that can be dynamically controlled by electric currents.The concept of symmetry pervades modern physics [ 1,2]. Through the conservation laws derived from various symmetries, high-level restrictions and selection rules can be derived for a variety of physical systems without any need for detailed investigations of their specific properties. Electromagnetic (EM) metamaterials [ 3,4,5] and, more specifically, Fano-resonant [ 6] metamaterials and meta-surfaces (FMs) [ 7,8,9,10,11,12,13,14,15] [ 20,21,22], dynamic tuning [ 23,24,25,26,27,28,25], and sensing and biosensing [ 29,30,31,32,33]. The spatial symmetries of electric charge distribution on the metamaterial's surface determine whether the EM resonance is "bright" (radiatively coupled to) or "dark" (radiatively de-coupled from) the EM continuum. As we demonstrate in this letter, other symmetries and their breaking can also be crucial to determine the properties of EM resonances and enable their mutual coupling, which in turn can give rise to EM Fano interferences.We consider a meta-surface formed by a two-dimensional array of double-antenna metamolecules [ 34] [ Fig.1(a)]. Such meta-molecules support two low-frequency resonances formed by hybridization of the dipolar modes of the individual antennas that have distinct symmetric and anti-symmetric charge/current distributions responsible for their strongly disparate radiative coupling. The scattering of light by the symmetric mode is dominated by the electric dipolar moment of the meta-molecules ( ) along the y-direction, leading to its strong radiative coupling and its "bright" character. The anti-symmetric mode, in contrast, is dominated by the magnetic dipolar ( ) and electric quadrupolar ( ) moments, leading to its "darkness", i.e. its complete decoupling from the normally incident EM wave [see Fig.1(b)]. Fano interference arises from the coupling between the symmetric and anti-symmetric resonances, which are a consequence of

Photonic topological Chern insulators based on Tellegen metacrystals

“…It bears mentioning that off-diagonal magnetoelectric coupling can be straightforwardly engineered in composites of piezoelectric and magnetic materials [40] where elastic forces mediate the coupling between electric and magnetic orders, however this feature limits their application to low frequencies. Putting aside the requirement of zero external bias allows one to consider metamaterial possibilities such as the one sketched in figure 1(a), in which omega-particle elements are used to couple the ac magnetic dipole moment of the double-wire metamolecule m (which corresponds to asymmetric mode of the antennas) and its ac electric dipole moment e zz (which corresponds to the symmetric mode of the antennas) through natural magneto-optical response of a ferrite sphere place in the center [41]. This proposal bears some relation to the concept in [36,41] and will not be investigated in detail, but supports the notion that a practical TPC design may be within reach.…”

“…Putting aside the requirement of zero external bias allows one to consider metamaterial possibilities such as the one sketched in figure 1(a), in which omega-particle elements are used to couple the ac magnetic dipole moment of the double-wire metamolecule m (which corresponds to asymmetric mode of the antennas) and its ac electric dipole moment e zz (which corresponds to the symmetric mode of the antennas) through natural magneto-optical response of a ferrite sphere place in the center [41]. This proposal bears some relation to the concept in [36,41] and will not be investigated in detail, but supports the notion that a practical TPC design may be within reach. In the following we focus on demonstrating the general concept leaving issues of implementation to the future.…”

Size-efficient metamaterial absorber at low frequencies: Design, fabrication, and characterization

“…MMs are known as artificial materials including both electric and magnetic components, which play role as artificial "atoms" or "molecules." These artificial elements are flexible and easily manipulated to provide many precious effects, such as negative refractive index, 1,2 slow light, [3][4][5] super resolutions, 6,7 and invisibility cloaking. 8,9 So far, many works relevant to MMs have been investigated in wide frequency range from radio, 10 microwave, 11 THz, 12 infrared 13 to visible.…”

Implementation of Electromagnetically Induced Transparency in a Metamaterial Controlled with Auxiliary Waves

“…On the other hand, when the resonant frequencies are different, the transparent region is located at the shoulder of the broad absorption profile and shows an asymmetrical shape [16,27,28], which is unique to the Fano resonance [29,30]. In addition to slow propagation, EIT-like metamaterials are applied to implementing various functionalities, such as accurate sensing [31][32][33], manipulation of near fields [34], nonreciprocal transmission [35,36], lasing spacers [37], and absorption enhancement [38].…”