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We determine the effective complex permittivity of a two-dimensional composite, consisting of an arbitrary doubly periodic array of identical circular cylinders in a homogeneous matrix, whose dielectric properties are complex-valued. Efficient formulas are provided to determine the effective complex permittivity tensor which are in excellent agreement with numerical calculations. We also show that...
A reconfigurable metamaterial terahertz filter based on graphene is presented and discussed. The device structure consists of periodic metallic rings with gaps, where graphene stripes are located. It is shown that the filter resonance frequency can easily be adjusted by varying the conductivity of graphene; this is practically implemented via changing the number of stacked graphene layers. Terahertz...
A continuously electrically tunable composite right/left-handed leaky-wave antenna based on liquid crystal is presented. Beam steering from −6° to 9° with respect to the broadside at a fixed operation frequency of 26.7 GHz is achieved by applying a tuning voltage between 0 V and 120 V. Far field measurements and the response times of the liquid crystal for this specific application are analyzed in...
In this contribution, we present a magnet-less non-reciprocal filtering module to be used in waveguide and antenna system for circular polarization applications. The filtering module, sandwiched between two thin dielectric slabs, consists of a annular aperture in a metallic screen which exhibits zero reflection, and thus maximum transmission, in a narrow frequency band around its resonant frequency...
This paper presents some guidelines to achieve wide bandwidth and low loss in the design of mu-negative medium consisting of SRR-type resonators through a structural change from an engineering point of view. The effective permeability for the single ring resonator (RR) medium is expressed in a very convenient form to facilitate the analysis of the bandwidth and losses by introducing appropriate structural...
The magneto-optical phase effects of a hybrid metal-dielectric structure are studied theoretically. An applied magnetic field alters the phase of transmitted and reflected waves. The effect demonstrates resonant behavior at the excitation of plasmonic eigenmodes in the transverse configuration. The conditions for the resonant enhancement of the effect are found.
We consider the hypersingular plasmonic surface modes that are supported by a 3D negative-permittivity circular conical tip and study how their occurrence depends on the opening angle and permittivity of the cone. A comparison to a 2D wedge is made.
We study the guided modes in the wire medium slab taking into account both the nonlocality and losses in the structure. We show that due to the fact that the wire medium is an extremeley spatially dispersive metamaterial, the effect of nonlocality plays a critical role since it results in coupling between the otherwise orthogonal guided modes. We show that such a structure supports a set of deep subwavelength...
We propose a general method to synthesize metasurfaces based on a polarizability-susceptibility scattering approach. We show that a minimal set of four non-zero effective electric and magnetic susceptibility tensor components is sufficient to theoretically transform an incident electromagnetic wave into a great diversity of transmitted and/or reflected waves, where the metasurface can provide positive...
In this work a technique for designing linear to circular polarization convertors is proposed. It is based on self-complementary metasurfaces graved on metal sheets. This kind of device can receive a linearly polarized wave and convert it into a circularly polarized wave. The main advantage over previous designs is the theoretical constancy of the phase difference between the transmission (or reflection)...
Here, two different THz radiating structures are analyzed, consisting both of a central slot surrounded by annular or straight corrugations. Concentrically grooved antenna presents a moderately high gain. Its radiation and temporal properties are analyzed both numerically and experimentally. For the second case, no appreciable differences in terms of radiation characteristics are observed when the...
Acoustic metamaterial elements based on cylindrical elastic shells with an internal mass supported by axisymmetric stiffeners are described. The shell's effective acoustic properties are tuned by varying the mass and stiffness. The elements can be impedance and index matched to water, resulting in near-zero scattering cross section over a broad range of low frequencies. The physical constraints necessary...
This paper presents an efficient and accurate approach for the analysis of anisotropic metasurfaces (MTSs) consisting of elliptical patches printed over a grounded slab. The formulation resorts to an analytical expression of the currents excited on the elements of the periodic texture to define a reduced spectral MoM procedure with only two basis functions. This procedure can be used to effectively...
Four different numerical methods for calculating the quality factor and resonance wavelength of a nano or micro photonic cavity are compared. Good agreement was found for a wide range of quality factors. Advantages and limitations of the different methods are discussed.
High impedance metasurfaces (HIMSs) formed by interwoven conductor arrays are proposed. Bandwidth comparable with that of the basic square patches is achieved at an order of magnitude smaller unit cells. The presented structures are apt for small mobile terminals and low frequency applications.
We introduce an expansion of the Fourier modal method for the analysis of periodic structures with oblique walls by using a three-dimensional normal vector field for the correct Fourier series factorization of products of discontinuous functions. Our numerical tests show that the improved method leads to faster convergence as compared to conventional two-dimensional decomposition rules.
We present a new concept of metasurfaces that vary the electromagnetic responses depending not only on the frequency of an incoming surface wave but also on the waveform. Such waveform selectivity is achieved by integrating the rectification of schottky diodes with time domain responses of capacitors and inductors. This new characteristic enables us to control electromagnetic waves a new manner, thus...
The optical spectra for a variety of single and coupled graphene nano-flakes have been studied using time-dependent density functional theory within generalized gradient approximation. The time evolution of the charge density induced by a continuous-wave electrical field excitation has been calculated as well, in order to investigate the plasmonic properties of these graphene nano-structures. For...
In this paper, the effects of placing a longitudinal slot in the channel region of a rectangular waveguide ENZ structure, are analyzed. A following investigation showed that changing the length of this slot can be employed to achieve tuning of only the tunneling frequency. Maximum resonant frequency shift reported is 11%. In addition, the equivalent circuit for the ENZ structure with this kind of...
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