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Ginis V.,Vrije Universiteit Brussel | Tassin P.,Chalmers University of Technology | Koschny T.,Iowa State University | Soukoulis C.M.,Iowa State University | Soukoulis C.M.,Institute of Electronic Structure and Lasers IESL
Applied Physics Letters | Year: 2016

Metasurfaces allow for advanced manipulation of optical signals by imposing phase discontinuities across flat interfaces. Unfortunately, these phase shifts remain restricted to values between 0 and 2π, limiting the delay-bandwidth product of such sheets. Here, we develop an analytical tool to design metasurfaces that mimic three-dimensional materials of arbitrary thickness. In this way, we demonstrate how large phase discontinuities can be realized by combining several subwavelength Lorentzian resonances in the unit cell of the surface. Our methods open up the temporal response of metasurfaces and may lead to the construction of metasurfaces with a plethora of new optical functions. © 2016 AIP Publishing LLC.

Ginis V.,Vrije Universiteit Brussel | Tassin P.,Iowa State University | Danckaert J.,Vrije Universiteit Brussel | Soukoulis C.M.,Iowa State University | And 2 more authors.
New Journal of Physics | Year: 2012

We investigate the potential of transformation optics for the design of novel electromagnetic cavities. First, we determine the dispersion relation of bound modes in a device performing an arbitrary radial coordinate transformation and we discuss a number of such cavity structures. Subsequently, we generalize our study to media that implement azimuthal transformations, and show that such transformations can manipulate the azimuthal mode number. Finally, we discuss how the combination of radial and azimuthal coordinate transformations allows for perfect confinement of subwavelength modes inside a cavity consisting of right-handed materials only. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Kurter C.,University of Maryland University College | Tassin P.,Iowa State University | Tassin P.,Vrije Universiteit Brussel | Zhuravel A.P.,Ukrainian Academy of Sciences | And 7 more authors.
Applied Physics Letters | Year: 2012

We demonstrate a nonlinear metamaterial that can be switched between low and high transmission by controlling the power level of the incident beam. The origin of this nonlinear response is the superconducting Nb thin film employed in the metamaterial structure. We show that with moderate RF power of about 22 dBm it is possible to quench the superconducting state as a result of extremely strong current densities at the corners of the metamaterial's split-ring resonators. We measure a transmission contrast of 10 dB and a change in group delay of 70 ns between the low and high power states. © 2012 American Institute of Physics.

Zhang L.,Iowa State University | Koschny T.,Iowa State University | Soukoulis C.M.,Iowa State University | Soukoulis C.M.,Institute of Electronic Structure and Lasers IESL
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Metamaterials are patterned metallic structures which permit access to a novel electromagnetic response, negative index of refraction, impossible to achieve with naturally occurring materials. Using the Babinet principle, the complementary split ring resonator (SRR) is etched in a metallic plate to provide negative ε, with perpendicular direction. Here we propose a new design, etched in a metallic plate to provide negative magnetic permeability μ, with perpendicular direction. The combined electromagnetic response of this planar metamaterial, where the negative μ comes from the aperture and the negative ε from the remainder of the continuous metallic plate, allows achievement of a double negative index metamaterial (NIM) with only one metasurface and strong transmission. These designs can be used to fabricate NIMs at microwave and optical wavelengths and three-dimensional metamaterials. © 2013 American Physical Society.

Tassin P.,Iowa State University | Koschny T.,Iowa State University | Soukoulis C.M.,Iowa State University | Soukoulis C.M.,Institute of Electronic Structure and Lasers IESL
Physica B: Condensed Matter | Year: 2012

An important tool in the field of metamaterials is the extraction of effective material parameters from simulated or measured scattering parameters of a sample. Here we discuss a retrieval method for thin-film structures that can be approximated by a two-dimensional scattering sheet. We determine the effective sheet conductivity from the scattering parameters and we point out the importance of the magnetic sheet current to avoid an overdetermined inversion problem. Subsequently, we present two applications of the sheet retrieval method. First, we determine the effective sheet conductivity of thin silver films and we compare the resulting conductivities with the sheet conductivity of graphene. Second, we apply the method to a cut-wire metamaterial with an electric dipole resonance. The method is valid for thin-film structures such as two-dimensional metamaterials and frequency-selective surfaces and can be easily generalized for anisotropic or chiral media. © 2012 Elsevier B.V.

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