Optical properties of Fano-resonant metallic metasurfaces on a substrate

Mousavi, S. Hossein; Khanikaev, Alexander B.; Shvets, Gennady

doi:10.1103/physrevb.85.155429

Cited by 24 publications

(20 citation statements)

References 57 publications

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“…One is shifting the resonance dips to low frequencies, which is due to the permittivity difference between air and silicon substrate37. The other effect is leading to Fano-type resonance profile, which is due to the coupling between the dipole resonance modes of the Maltese cross and the Fabry–Pérot mode of the substrate38. The resonance frequency shifts shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy

et al. 2012

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Dichroic polarizers and waveplates exploiting anisotropic materials have vast applications in displays and numerous optical components, such as filters, beamsplitters and isolators. Artificial anisotropic media were recently suggested for the realization of negative refraction, cloaking, hyperlenses, and controlling luminescence. However, extending these applications into the terahertz domain is hampered by a lack of natural anisotropic media, while artificial metamaterials offer a strong engineered anisotropic response. Here we demonstrate a terahertz metamaterial with anisotropy tunable from positive to negative values. It is based on the Maltese-cross pattern, where anisotropy is induced by breaking the four-fold symmetry of the cross by displacing one of its beams. The symmetry breaking permits the excitation of a Fano mode active for one of the polarization eigenstates controlled by actuators using microelectromechanical systems. The metamaterial offers new opportunities for the development of terahertz variable waveplates, tunable filters and polarimetry.

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Section: Resultsmentioning

confidence: 97%

Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy

et al. 2012

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“…Such coupling of multipolar moments makes the meta-molecules bianisotropic and occurs when the spatial symmetry of the meta-molecules is reduced [ 36]. Two well-known mechanisms to induce bianisotropy is by breaking of spatial symmetry: i) intrinsic [ 9,7,17], when the meta-molecule's geometry is distorted, e.g., by making the antennas unequal [ 7,16,33]), and, ii) extrinsic, by utilizing obliquely incident waves with finite component of wavenumber in the x-direction [ 37,38,39,40]). In this letter, we propose a third symmetry-breaking mechanism of inducing magneto-electric coupling.…”

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confidence: 99%

“…and the transmission coefficient is calculated as K 1 + A [ 50,38] assuming an infinitely thin electric metasurface [ 53]. It follows from Eq.…”

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confidence: 99%

Gyromagnetically Induced Transparency of Metasurfaces

et al. 2014

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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

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“…Optical force on graphene is simply the electromagnetic force exerted on the surface currents and surface charges carried by this thin film. However, using the Coulomb-Lorentz force law to evaluate the force is only accurate when graphene weakly perturbs the system, because a graphene sheet in any optical system introduces discontinuities to the electromagnetic fields surrounding it, and renders the field terms in the Coulomb-Lorentz force ill-defined ( Fig.1b) H ‖ is inconsequential only when the surface conductivity  is much smaller than the characteristic admittance [43][44][45] of the surrounding medium 1 Y (see Supporting Info S1 and S2). For graphene, this condition is satisfied in near-infrared and visible wavelengths (see Supporting Info S3).…”

Section: Perturbative Treatment Using the Coulomb-lorentz Force Lawmentioning

confidence: 99%

Strong THz and Infrared Optical Forces on a Suspended Single-Layer Graphene Sheet

2014

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Single-layer graphene exhibits exceptional mechanical properties attractive for optomechanics: it combines low mass density, large tensile modulus, and low bending stiffness. However, at visible wavelengths, graphene absorbs weakly and reflects even less, thereby inadequate to generate large optical forces needed in optomechanics. Here, we numerically show that a single-layer graphene sheet is sufficient to produce strong optical forces under terahertz or infrared illumination. For a system as simple as graphene suspended atop a uniform substrate, high reflectivity from the substrate is crucial in creating a standing-wave pattern, leading to a strong optical force on graphene. This force is readily tunable in amplitude and direction by adjusting the suspension height. In particular, repellent optical forces can levitate graphene to a series of stable equilibrium heights above the substrate. One of the key parameters to maximize the optical force is the excitation frequency: peak forces are found near the scattering frequency of free carriers in graphene. With a dynamically controllable Fermi level, graphene opens up new possibilities of tunable nanoscale optomechanical devices.Graphene interacts with light in unusual ways: while it is virtually invisible to light polarized normal to its surface, it interacts strongly with THz and mid-infrared light polarized parallel to its surface, even though it is only a monolayer of atoms 1-9 . This interaction is highly frequencydependent due to the interband and intraband transitions of the free carriers in graphene 2,10-12 . The collective oscillations of these free carriers can also produce nanoscale plasmons, enabling the confinement of light to dimensions much smaller than the light wavelength [13][14][15][16][17] . Meanwhile, graphene possesses several attractive mechanical properties 18 : as a single atomic layer, graphene has very low mass density; while a free flake of graphene can be easily bent 19,20 , it has an exceptionally stiff in-plane Young's modulus ~1 TPa 21 . On the surface with another material, it behaves like a fluidic interface and readily conforms, thanks to a remarkably strong adhesion with large Van der Waals forces on the order of 1 GPa 22,23 .

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Optical properties of Fano-resonant metallic metasurfaces on a substrate

Cited by 24 publications

References 57 publications

Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy

Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy

Gyromagnetically Induced Transparency of Metasurfaces

Strong THz and Infrared Optical Forces on a Suspended Single-Layer Graphene Sheet

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