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In analogy with spatial multilayers, we put forward the idea of Herpin equivalence in temporal metamaterials characterized by step-like time variations of the constitutive parameters. We show that, at a given frequency, an arbitrary temporal multistep exhibiting mirror symmetry can be replaced by an equivalent temporal slab with suitable refractive index and travel-time. This enables the synthesis of arbitrary values of the refractive index, in a way that differs fundamentally from the effective-medium approach, and adds new useful analytical machinery to the available toolbox for the study and design of temporal metamaterials, with potentially intriguing applications to anti-reflection coatings and filters.

Multisection quarter-wave impedance transformers are widely applied in microwave engineering and optics to attain impedance-matching networks and antireflection coatings. These structures are mostly designed in the spatial domain (time harmonic) by using geometries of different materials. Here, we exploit such concepts in the time domain by using time-varying metamaterials. We derive a formal analogy between the spectral responses of these structures and their temporal analogs, i.e., time-varying stepped refractive-index profiles. We show that such space-time duality grants access to the vast arsenal of synthesis approaches available in microwave engineering and optics. This allows, for instance, the synthesis of temporal impedance transformers for broadband impedance matching with maximally flat or equi-ripple responses, which extend and generalize the recently proposed quarter-wave design as an antireflection temporal coating. Our results, validated via full-wave numerical simulations, provide new insights and deeper understanding of the wave dynamics in time-varying media, and may find important applications in space-time metastructures for broadband frequency conversion and analog signal processing.

Metamaterials are mostly designed in the time-harmonic scenario where wave propagation can be spatially manipulated. Tailoring the electromagnetic response of media in time has also gained the attention of the scientific community in order to achieve further control on wave-matter interaction both in space and time. In the present work, a temporally effective medium concept in metamaterial is theoretically investigated as a mechanism to create a medium with a desired effective permittivity. Similar to spatially subwavelength multilayered metamaterials, the proposed “temporal multilayered”, or “multistepped” metamaterial, is designed by alternating in time the permittivity of the medium between two values. In so doing, the temporally periodic medium can be modeled as an effective metamaterial in time with an effective permittivity initiated by a step function. The analogy between the temporal multistepped and the spatial multilayered metamaterials is presented demonstrating the duality between both domains. The proposed temporal metamaterial is analytically and numerically evaluated showing an excellent agreement with the designed parameters. Moreover, it is shown how the effective permittivity can be arbitrarily tailored by changing the duty cycle of the periodic temporal metamaterial. This performance is also connected to the spatial multilayer scenario in terms of the filling fraction of the different materials used to create the multilayered structures.

Optomechanics deals with the control and applications of mechanical effects of light that stems from the redistribution of photon momenta in light scattering. As an example, light-induced levitation of an infinitesimally small dipolar particle is expected in front of epsilon-near-zero (ENZ) metamaterials. However, a theoretical understanding of these effects on single-material and multi-material larger particles is still lacking. Here, we investigate, analytically and numerically, optical forces on polarizable particles with size ranging from 20 nm to a 1 μm in proximity of ENZ metamaterials. We look at the general features of the repulsive-attractive optomechanics from the nano to the microscale exploiting different theoretical methods (dipole approximation, finite elements calculations, transition (T-)matrix). We discuss the role of realistic layered materials, as our ENZ substrate, on optical forces and analyze the influence of composition and shape by studying a range of complex particles (dielectric, core-shell, plasmonic ellipsoids). Physical insights into the results are discussed and future research directions are forecasted. Our results provide possibilities in exploiting engineered materials and surfaces for the manipulation and tailoring of light-induced forces in optomechanics. Optomechanics deals with the control and applications of mechanical effects of light on matter. Here, these effects on single-material and multimaterial larger particles with size ranging from 20 nm to a 1 μm are investigated in proximity of epsilon-near-zero metamaterials exploiting different theoretical methods. [ABSTRACT FROM AUTHOR]

Recently, it has been shown that temporal metamaterials based on impulsive modulations of the constitutive parameters (of duration much smaller than a characteristic electromagnetic timescale) may exhibit a nonlocal response that can be harnessed so as to perform elementary analog computing on an impinging wavepacket. These short-pulsed metamaterials can be viewed as the temporal analog of conventional (spatial) metasurfaces. Here, inspired by the analogy with cascaded metasurfaces, we leverage this concept and take it one step further, by showing that short-pulsed metamaterials can be utilized as elementary bricks for more complex computations. To this aim, we develop a simple, approximate approach to systematically model the multiple actions of time-resolved short-pulsed metamaterials. Via a number of representative examples, we illustrate the computational capabilities enabled by this approach, in terms of simple and composed operations, and validate it against a rigorous numerical solution. Our results indicate that the temporal dimension may provide new degrees of freedom and design approaches in the emerging field of computational metamaterials, in addition or as an alternative to conventional spatially variant platforms. [ABSTRACT FROM AUTHOR]

In this Letter, an all metallic sensor based on ε-near-zero (ENZ) metamaterials is studied both numerically and experimentally when working at microwave frequencies. To emulate an ENZ medium, a sensor is made by using a narrow hollow rectangular waveguide, working near the cutoff frequency of its fundamental TE10 mode. The performance of the sensor is systematically evaluated by placing subwavelength dielectric analytes (with different sizes and relative permittivities) within the ENZ waveguide and moving them along the propagation and transversal axes. It is experimentally demonstrated how this ENZ sensor is able to detect deeply subwavelength dielectric bodies of sizes up to 0.04λ and height 5 × 10−3 λ with high sensitivities (and the figure of merit) up to 0.05 1/RIU (∼0.6 GHz−1) and 0.6 1/RIU when considering the sensor working as a frequency- or amplitude-shift-based device, respectively. [ABSTRACT FROM AUTHOR]

In this brief opinionated article, I present a personal perspective on metamterials with high degrees of freedom and dimensionality and discuss their potential roles in enriching light–matter interaction in photonics and related fields. [ABSTRACT FROM AUTHOR]

The process of diffusion is central to the ever increasing entropic state of the universe and is fundamental in many branches of science and engineering. Although non-reciprocal metamaterials are well developed for wave systems, the studies of diffusive metamaterials have been limited by their characteristic spatial inversion symmetry and time inversion antisymmetry. Here, we achieve large spatial asymmetric diffusion characteristics inside a metamaterial whose material parameters are space- and time-modulated. Inside such a spatiotemporal metamaterial, diffusion occurs as if the material had an intrinsic flow velocity, whose direction is dictated by the relative phase between the modulations of the conductivity and capacity. This creates dramatic out-of-equilibrium concentrations and depletions, which we demonstrate experimentally for the diffusion of electric charges in a one-dimensional electrical system composed of an array of space-time-modulated variable capacitors and switches. These results may offer exciting possibilities in various fields, including electronics, thermal management, chemical mixing, etc. Being able to manipulate the temporal evolution and spatial distribution of diffusive quantities would provide exciting possibilities for applications. Here, the authors show that one can achieve large spatial asymmetric diffusion characteristics inside a metamaterial whose material parameters are space- and time-modulated. [ABSTRACT FROM AUTHOR]

In solid-state physics, "doping" is a pivotal concept that allows controlling and engineering of the macroscopic electronic and optical properties of materials such as semiconductors by judiciously introducing small concentrations of impurities. Recently, this concept has been translated to two-dimensional photonic scenarios in connection with host media characterized by vanishingly small relative permittivity ("epsilon near zero"), showing that it is possible to obtain broadly tunable effective magnetic responses by introducing a single, nonmagnetic doping particle at an arbitrary position. So far, this phenomenon has been studied mostly for lossless configurations. In principle, the inevitable presence of material losses can be compensated via optical gain. However, taking inspiration from quantum (e.g., parity-time) symmetries that are eliciting growing attention in the emerging fields of non-Hermitian optics and photonics, this suggests considering more general gain-loss interactions. Here, we theoretically show that the photonic doping concept can be extended to non-Hermitian scenarios characterized by tailored distributions of gain and loss in either the doping particles or the host medium. In these scenarios, the effective permeability can be modeled as a complex-valued quantity (with the imaginary part accounting for the gain or loss), which can be tailored over broad regions of the complex plane. This enables a variety of unconventional optical responses and waveguiding mechanisms, which can be, in principle, reconfigured by varying the optical gain (e.g., via optical pumping). We envision several possible applications of this concept, including reconfigurable nanophotonics platforms and optical sensing, which motivate further studies for their experimental validation. [ABSTRACT FROM AUTHOR]

The notion of artificially engineered materials, which has a long history dating back to the late part of the 19th century, gained considerable momentum two decades ago. The excitement associated with such metamaterials and the structures they have inspired has not waned since then. Rather, it has substantially grown. Metamaterial-inspired structures continue to challenge our imagination and our physics and engineering foundations. They are impacting wave–matter interactions across many frequencies and even across diverse fields of science and technology. They are now enabling many commercial opportunities. It is anticipated that they will provide access to yet new physical phenomena and will facilitate many novel future applications. [ABSTRACT FROM AUTHOR]

The article discusses that the developments in the field of metamaterials and metasurfaces have renewed growing interest in light–matter interaction in four-dimensional metamaterials. Merging spatial and temporal interfaces may open a new horizon in four-dimensional optics, in which some of the features of both interfaces can be exploited, such as mixing amplitude and frequency modulations.

The control and manipulation of thermal fields is a key scientific and technological challenge, usually addressed with nanophotonic structures with a carefully designed geometry. Here, we theoretically investigate a different strategy based on epsilon-near-zero (ENZ) media. We demonstrate that thermal emission from ENZ bodies is characterized by the excitation of spatially static fluctuating fields, which can be resonantly enhanced with the addition of dielectric particles. The "spatially static" character of these temporally dynamic fields leads to enhanced spatial coherence on the surface of the body, resulting in directive thermal emission. By contrast with other approaches, this property is intrinsic to ENZ media and it is not tied to its geometry. This point is illustrated with effects such as geometry-invariant resonant emission, beamforming by boundary deformation, and independence with respect to the position of internal particles. We numerically investigate a practical implementation based on a silicon carbide body containing a germanium rod. [ABSTRACT FROM AUTHOR]

Surface plasmons polaritons are collective excitations of an electron gas that occur at an interface between negative-ε and positive-ε media. Here, we report the experimental observation of such surface waves using simple waveguide metamaterials filled only with available positive-ε media at microwave frequencies. In contrast to optical designs, in our setup the propagation length of the surface plasmons can be rather long as low loss conventional dielectrics are chosen to avoid typical losses from negative-ε media. Plasmonic phenomena have potential applications in enhancing light– matter interactions, implementing nanoscale photonic circuits and integrated photonics. [ABSTRACT FROM AUTHOR]

Doping a semiconductor with foreign atoms enables the control of its electrical and optical properties. We transplant the concept of doping to macroscopic photonics, demonstrating that two-dimensional dielectric particles immersed in a two-dimensional epsilon-near-zero medium act as dopants that modify the medium's effective permeability while keeping its effective permittivity near zero, independently of their positions within the host. The response of a large body can be tuned with a single impurity, including cases such as engineering perfect magnetic conductor and epsilon-and-mu-near-zero media with nonmagnetic constituents. This effect is experimentally demonstrated at microwave frequencies via the observation of geometry-independent tunneling. This methodology might provide a new pathway for engineering electromagnetic metamaterials and reconfigurable optical systems. [ABSTRACT FROM AUTHOR]

One of the most promising and vibrant research areas in nanotechnology has been the field of metasurfaces. These are two dimensional representations of metaatoms, or artificial interfaces designed to possess specialized electromagnetic properties which do not occur in nature, for specific applications. In this article, we present a brief review of metasurfaces from a materials perspective, and examine how the choice of different materials impact functionalities ranging from operating bandwidth to efficiencies. We place particular emphasis on emerging and non-traditional materials for metasurfaces such as high index dielectrics, topological insulators and digital metamaterials, and the potentially transformative role they could play in shaping further advances in the field. [ABSTRACT FROM AUTHOR]

Vacuum fluctuations are one of the most distinctive aspects of quantum optics, being the trigger of multiple nonclassical phenomena. Thus, platforms like resonant cavities and photonic crystals that enable the inhibition and manipulation of vacuum fluctuations have been key to our ability to control light-matter interactions (e.g., the decay of quantum emitters). Here, we theoretically demonstrate that vacuum fluctuations may be naturally inhibited within bodies immersed in epsilon-and-mu-near-zero (EMNZ) media, while they can also be selectively excited via bound eigenmodes. Therefore, zero-index structures are proposed as an alternative platform to manipulate the decay of quantum emitters, possibly leading to the exploration of qualitatively different dynamics. For example, a direct modulation of the vacuum Rabi frequency is obtained by deforming the EMNZ region without detuning a bound eigenmode. Ideas for the possible implementation of these concepts using synthetic implementations based on structural dispersion are also proposed. [ABSTRACT FROM AUTHOR]

Ebrahim I et al. i [3] investigate the temporal dynamics in strongly coupled ENZ plasmonic systems, illustrating the dynamics of field enhancement processes and highlighting the impact of dissipation loss. Beruete I et al. i [14] demonstrate experimentally the unusual waveguiding features of zero-permittivity structures with applications for enhanced sensing, and in parallel, Nicolussi I et al. i [15] discuss unusual unidirectional transparency in waveguides featuring zero-permittivity materials obeying parity-time symmetry. Zero-index metamaterials (photonic materials and artificial media with a near-zero refractive index in different parts of the electromagnetic spectrum) make possible novel forms of light-matter interactions where light behaves in a qualitatively different way than in conventional materials. [Extracted from the article]

Efficient and accurate computer simulation of wave phenomena plays an important role in invention, development, cost reduction and optimization of many systems ranging from ultra-high-speed electronics to delicate nanoscale optical devices and systems. Understanding the physics of many modern technological applications such as optical nanomaterials calls for the solution of very complex computer models involving hundreds of millions to billions of unknowns. Integral equation (IE) methods are increasingly becoming the method of choice when comes to numerical modeling of wave phenomena for various reasons specifically since the introduction of FMM and MLFMA acceleration that tremendously reduce the computational costs associate with naive implementation of IE methods. In this work, a new acceleration technique specifically designed for the modeling of large, inhomogeneous, finite array problems it introduced. Specifically we use the new method for modelling and design of some metamaterial structures. At last, the presented method is used to study the some of the undesired random effects that occur in metamaterial array fabrication. [ABSTRACT FROM AUTHOR]

The performance of an epsilon-near zero (ENZ) plano-concave lens is experimentally demonstrated and verified at the D-band of the millimeter-waves. The lens is comprised of an array of narrow metallic waveguides near cut-off frequency, which effectively behaves as an epsilon-near-zero medium at 144 GHz. A good matching with free space is achieved by exploiting the phenomenon of energy squeezing and a clear focus with a transmission enhancement of 15.9 dB is measured. The lens shows good radiation properties with a directivity of 17.6 dBi and low cross-polar components of -34 dB. All results are supported by numerical simulations. [ABSTRACT FROM PUBLISHER]

Balancing complexity and simplicity has played an important role in the development of many fields in science and engineering. One of the well-known and powerful examples of such balance can be found in Boolean algebra and its impact on the birth of digital electronics and the digital information age. The simplicity of using only two numbers, '0' and '1', in a binary system for describing an arbitrary quantity made the fields of digital electronics and digital signal processing powerful and ubiquitous. Here, inspired by the binary concept, we propose to develop the notion of digital metamaterials. Specifically, we investigate how one can synthesize an electromagnetic metamaterial with a desired permittivity, using as building blocks only two elemental materials, which we call 'metamaterial bits', with two distinct permittivity functions. We demonstrate, analytically and numerically, how proper spatial mixtures of such metamaterial bits lead to elemental 'metamaterial bytes' with effective material parameters that are different from the parameters of the metamaterial bits. We then apply this methodology to several design examples of optical elements, such as digital convex lenses, flat graded-index digital lenses, digital constructs for epsilon-near-zero (ENZ) supercoupling and digital hyperlenses, thus highlighting the power and simplicity of the methodology. [ABSTRACT FROM AUTHOR]

We study propagation of transverse-magnetic electromagnetic waves in the bulk and at the surface of a magnetized epsilon-near-zero (ENZ) medium in a Voigt configuration. We reveal that in a certain range of material parameters novel regimes of wave propagation emerge; we show that the transparency of the medium can be altered with the magnetization leading either to magnetically induced Hall opacity or Hall transparency of the ENZ. In our theoretical study, we demonstrate that surface waves at the interface between either a transparent or an opaque Hall medium and a homogeneous medium may, under certain conditions, be predominantly one way. Moreover, we predict that one-way photonic surface states may exist at the interface of an opaque Hall ENZ and a regular metal, giving rise to the possibility for backscattenng immune wave propagation and isolation. [ABSTRACT FROM AUTHOR]

Optical materials with a dielectric constant near zero have the unique property that light advances with almost no phase advance. Although such materials have been made artificially in the microwave and far-infrared spectral range, bulk three-dimensional epsilon-near-zero (ENZ) engineered materials in the visible spectral range have been elusive. Here, we present an optical metamaterial composed of a carefully sculpted parallel array of subwavelength silver and silicon nitride nanolamellae that shows a vanishing effective permittivity, as demonstrated by interferometry. Good impedance matching and high optical transmission are demonstrated. The ENZ condition can be tuned over the entire visible spectral range by varying the geometry, and may enable novel micro/nanooptical components, for example, transmission enhancement, wavefront shaping, controlled spontaneous emission and superradiance. [ABSTRACT FROM AUTHOR]

We present an analytical model and practical design tools to realize cylindrically-symmetric compact antennas based on the anomalous transmission properties of \varepsilon-near-zero (ENZ) ultranarrow radial channels. The flexibility and exotic propagation properties in ENZ metamaterial channels are exploited here to tune and match cylindrically-symmetric antennas, without the need of complex external matching networks, in order to realize exciting antenna designs in terms of size, complexity and efficiency. We first model a homogenized Drude dispersive ENZ metamaterial channel to feed a radial parallel-plate waveguide; next we suggest a practical realization of this channel by using radial fins; eventually, we apply the obtained design formulas to realize single- and multi-band cylindrical antennas with a wide tunability range. The designed antennas may operate in the ultra-high frequency (UHF) band and may be realistically tuned over a large bandwidth. We envision applications in frequency-hopping, multi-band, compact, omnidirectional antennas. [ABSTRACT FROM PUBLISHER]

Based on an analogy with electromagnetic metamaterials, we develop an effective medium description for the propagation of electron matter waves in bulk semiconductors with a zinc-blende structure. It is formally demonstrated that even though departing from a different starting point, our theory gives results for the energy stationary states consistent with Bastard's envelope-function approximation in the long-wavelength limit. Using the proposed approach, we discuss the time evolution of a wave packet in a bulk semiconductor with a zero-gap and linear energy-momentum dispersion. [ABSTRACT FROM AUTHOR]

Electric displacement current is present in capacitors and optical waveguides; however, unlike the conduction current in metallic wires, it is not confined. Analogous to the contrast in conductivity between a metallic wire and the surrounding air, displacement-current wires based on near-zero permittivity media contain a large contrast in effective permittivity. As a variation on this idea, in this Letter, we demonstrate at microwave frequencies two displacement-current cables based on effectively negative and effectively positive permittivity metastructures. Our experimental results clearly show cablelike behaviors that allow bending of the structure while still confining and maintaining the primarily longitudinal forward and reverse effective displacement currents within each conduit. The results presented here experimentally verify the notion of displacement-current wires and cables in metatronics as metamaterial-inspired circuitry. [ABSTRACT FROM AUTHOR]

The integration of radiofrequency electronic methodologies on micro- as well as nanoscale platforms is crucial for information processing and data-storage technologies. In electronics, radiofrequency signals are controlled and manipulated by 'lumped' circuit elements, such as resistors, inductors and capacitors. In earlier work, we theoretically proposed that optical nanostructures, when properly designed and judiciously arranged, could behave as nanoscale lumped circuit elements-but at optical frequencies. Here, for the first time we experimentally demonstrate a two-dimensional optical nanocircuit at mid-infrared wavelengths. With the guidance of circuit theory, we design and fabricate arrays of Si3N4 nanorods with specific deep subwavelength cross-sections, quantitatively evaluate their equivalent impedance as lumped circuit elements in the mid-infrared regime, and by Fourier transform infrared spectroscopy show that these nanostructures can indeed function as two-dimensional optical lumped circuit elements. We further show that the connections among nanocircuit elements, in particular whether they are in series or in parallel combination, can be controlled by the polarization of impinging optical signals, realizing the notion of 'stereo-circuitry' in metatronics-metamaterials-inspired optical circuitry. [ABSTRACT FROM AUTHOR]

Here we review the application of the optical nanocircuit paradigm to design and characterize metamaterials with exotic optical properties. The interaction of small nanoparticles with light is equivalently described in terms of optical lumped circuit elements, which relate the equivalent optical voltage across the particles and the optical displacement field current circulating through them. This equivalence goes beyond a simple description of the interaction of an individual nanoparticle with the impinging optical signal, as collections of closely spaced particles may be tailored as complex nanocircuit connections with specific optical response. Inspired by the fascinating concept and potentials of transmission-line metamaterials at microwaves, in which networks of lumped radio-frequency (RF) and microwave circuit elements may provide exotic metamaterial properties, in this paper, we review and discuss how analogous concepts may be translated to optical frequencies at the nanoscale, by applying the nanocircuit paradigm. We present several designs of 0-D, 1-D, 2-D, and 3-D arrays of nanoparticles supporting subwavelength resonances, negative-index propagation, and other exotic optical effects, achieved by suitably combining and connecting nanoparticles operating as optical lumped nanocircuit elements. Fascinating applications of these concepts are proposed in a variety of optical scenarios, considering the influence of natural material dispersion and loss in optical materials. [ABSTRACT FROM PUBLISHER]

Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a one-atom-thick platform for infrared metamaterials and transformation optical devices. Varying the graphene chemical potential by using static electric field yields a way to tune the graphene conductivity in the terahertz and infrared frequencies. Such degree of freedom provides the prospect of having different "patches" with different conductivities on a single flake of graphene. Numerous photonic functions and metamaterial concepts can be expected to follow from such a platform. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we discuss the analytical modeling of single and cascaded plasmonic metasurfaces excited by normally incident plane waves using a transmission-line shunt admittance model. We derive an analytical model that relates the effective surface optical admittance of a single metasurface to its inclusion polarizability and its plane wave reflection and transmission coefficients, and we apply these concepts to predict the wave interaction of more complicated setups in which two stacked surfaces are separated by a varying distance, and possibly rotated with respect to one another, for normal incidence excitation. We show that the analytical model holds very well under suitable conditions, and we verify our analytical results with full-wave numerical simulations, including material dispersion and loss of optical materials. [Copyright &y& Elsevier]

Enhancement of molecular emission is usually obtained by coupling small optical emitters with external resonant structures and systems, as first established by Purcell several decades ago, and verified in several recent investigations using molecules or quantum dots coupled with plasmonic nanoantennas. Here we theoretically investigate in detail a different mechanism for emission enhancement, based on our recent idea of a plasmonic nanolauncher [Phys. Rev. Lett. 2009, 103, 043902], i.e., a metamaterial-inspired ultranarrow waveguide channel operating near its cut-off frequency. Such system is not necessarily at resonance, but its peculiar operation may provide enhanced emission over a relatively broad physical area, which may allow enhancement of emission independent of the position of an individual or of a group of molecules along such plasmonic channel, and the possibility to bend and route the emitted energy with large flexibility. We present here extensive theoretical and numerical results that confirm this intuition and may envision a novel method for molecular emission enhancement at the nanoscale, with more flexibility than the conventional Purcell resonance techniques. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution, we discuss the possibility of applying the scattering-cancellation-based plasmonic cloaking technique to reduce the scattering from a sensing device, lowering its disturbance on sensing without affecting its ability to measure and “sense” the external world. The plasmonic cloak, while allowing the external fields to penetrate into the cover, may be able to suppress the scattering without necessarily shielding its interiors from the impinging light, which may be of great use if we wish to “sense” the external world, or receive an external signal, from inside the cloak. Our results may provide a unique sensing system that may receive and transmit signals, while its presence may not be perceived by the surrounding. This may be of great importance in a wide range of biological, optical, physical and engineering applications. [ABSTRACT FROM AUTHOR]

We propose the use of metamaterial-inspired ultranarrow channels at cutoff to realize an interesting matching between a coaxial antenna and a waveguide. The anomalous properties of a channel at cutoff, analogous to those of zero permittivity materials, allow a simple matching design, valid for arbitrary waveguides, with large degrees of freedom in terms of geometry, length and possible bending of the connecting channel. Moreover, the static-like properties of the channel allow such matching, independent of the relative position of the antenna and possible bending and abruptions along the channel. [ABSTRACT FROM AUTHOR]

In this article, we analyze the dispersion features of cloaking structures formed by plasmonic materials and/or metamaterials. Following our recent proposal for realizing a cloaking metamaterial shell capable of drastically suppressing the total scattering of moderately-sized objects, we investigate the frequency response and dispersion behavior of this anomalous phenomenon. Insights into the scattering reduction and possibility of multi-frequency response are presented, considering the inherent dispersion constraints of passive materials. [ABSTRACT FROM AUTHOR]

Here, we explore theoretically the concept of enhanced directivity from electrically small subwavelength radiators containing negative-parameter materials, such as plasmonic materials with negative permittivity at THz, infrared and optical frequencies. In particular, we study higher order plasmonic resonances of a subwavelength core-shell spherical nano-antenna, and we analyze the near-zone field distributions and far-field radiation patterns of such a structure when it is excited by a small dipole source, demonstrating analytically and numerically the possibility of having highly directive patterns from a nano-structure with electrically small dimensions. Radiation characteristics and intrinsic limitations on performance are analyzed in detail, and a potential application of this novel technique for super-resolution detection of the displacement of a nano-object is also pointed out. [ABSTRACT FROM AUTHOR]

Through experimental investigation, a thin subwave-length cavity resonator was physically realized using a bilayer structure composed of air and a negative permeability metamaterial structure one unit cell in thickness. We designed and built the metamaterial slab with periodic metallic ring structures and measured the spatial electric field magnitude in a cavity formed from this slab and a region of air, showing that a subwavelength cavity can be realized. The measured electric field magnitude distribution in the cavity matched very well with effective medium theory, showing that even a slab one unit cell in thickness may be effectively equivalent to a thin homogeneous medium as far as the construction of a sub-wavelength cavity is concerned, provided that the unit cell size is significantly smaller than the free space wavelength. [ABSTRACT FROM AUTHOR]

The detailed theory of a single subwavelength conformal radiator that exploits the resonant properties of thin cylindrical metamaterial shells supporting leaky waves is presented. It is shown and reviewed analytically and numerically how a circularly symmetric resonant leaky mode may be supported by a properly designed subwavelength homogenous cylindrical shell of low negative permittivity. Some physical insights are provided and numerical simulations with a feed point, considering also the finiteness of the antenna in the longitudinal direction, are presented and discussed. Moreover, possibilities and limitations of a practical realization of this setup are mentioned, considering in details the possible anisotropies in the metamaterials. [ABSTRACT FROM AUTHOR]

The potential use of metamaterial planar bilayers for synthesizing compact subwavelength leaky-wave radiators in the microwave regime is analyzed in detail. In particular, the possibility of pairing "complementary" metamaterials in order to reduce the dimensions of microwave components is explored for the leaky-wave operation of an open waveguide consisting of a grounded pair of planar layers. In connection with our similar findings in other setups employing such complementary pairings, here we show how the compact resonance at the interface between "negative" and "positive" materials may also be properly exploited in this context. Choosing materials with low constitutive parameters, moreover, shows to be effective for enhancing the directivity of these components. We explore in detail the notable guidance and radiation properties of the anomalous natural modes supported by these bilayered structures, giving some physical insights into the anomalous phenomenon and considering the possible limitations in some realistic setups. [ABSTRACT FROM AUTHOR]

We analyze the matching and radiation properties of subwavelength resonant patch antennas filled with double-negative, double-positive, and/or single-negative metamaterial blocks. Analyzing the theoretical limits inherently present when loading such common radiators with metamaterials, we show how these configurations may exhibit in principle an arbitrarily low resonant frequency for a fixed dimension, but they may not necessarily radiate efficiently when their size is electrically small. However, interesting possibilities are suggested to overcome these limitations by employing circular or more complex patch geometries in order to select specific modes that, when appropriate loading ratios between the filling materials are chosen, also ensure radiation performance comparable qualitatively with a regular patch radiator of standard dimensions. Realistic numerical simulations, considering material dispersion, losses and the presence of the antenna feed are presented, showing how a practical realization is foreseeable. This may open novel venues in the design of small-scaled radiators with enhanced performance, which is of interest for many applications. [ABSTRACT FROM AUTHOR]

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This article deals with a study of novel classes of metamaterial inclusions based on space-filling curves. The graph–theoretic Hamiltonian-path (HP) concept is exploited to construct a fairly broad class of space-filling curve geometries that include as special cases the well-known Hilbert an Peano curves whose application to metamaterial inclusions has recently been proposed. In this framework, the basic properties of HP are briefly reviewed, and a full-wave study of the electromagnetic properties of representative grid-graph HP geometries is carried out. Applications to metamaterial inclusions are explored, with focus on artificial magnetic conductors with reduced polarization-sensitivity. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2520–2524, 2006; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.21982 [ABSTRACT FROM AUTHOR]

Recently, there has been an increased interest in the problem of wave transmission through sub-wavelength apertures, following successful experimental demonstration by several groups for enhancing optical power transmission through nano-scale holes in metallic screens due to properly designed periodic corrugation. Oliner, Jackson, and their co-workers explained and justified this phenomenon as the result of the excitation of the leaky waves supported by the corrugated screen. Here we discuss in detail the mechanism and analysis for another setup we have recently proposed, in which metamaterial layers with special parameters may be utilized as covers over a single sub-wavelength aperture in a perfectly electric conducting (PEC) flat screen in order to increase the wave transmission through this aperture, and we provide a detailed physical insights and analytical explanation for this aperture setup that may lead to similar, potentially even more pronounced effects when the proper metamaterial layers are used in the entrance and the exit face of the hole in the flat PEC screen with no corrugation. Some numerical results confirming this theory are presented and discussed. We also investigate the sensitivity of the transmission enhancement to the geometrical and electromagnetic parameters of this structure. [ABSTRACT FROM AUTHOR]

In this paper, we address the issue of Foster's reactance theorem for the material media in which one or both of the material parameters ℇ and μ may possess negative real parts. We demonstrate that this theorem is indeed satisfied for a one-port termination filled with a lossless metamaterial with negative real permittivity and permeability, known as a double-negative (DNG) medium, or with a lossless metamaterial with either negative real permittivity or negative real permeability, which can be called a single-negative (SNG) medium. However, in the case of DNG media when the reactive input impedance of such a termination is compared with that of its counterpart filled with a conventional lossless double-positive (DPS) material, it is found that the two reactances have opposite signs. Similar conclusions can be made for a termination filled with a lossless epsilon-negative (ENG) material when it is compared with that of its mu-negative (MNG) counterpart. Therefore, if a one-port termination filled with a lossless DPS or ENG material possesses inductive input reactance, when the same termination is filled instead with a lossless DNG or MNG material, its input reactance may be capacitive. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 11–14, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11111 [ABSTRACT FROM AUTHOR]

Focuses on research advances in the metamaterial areas. Assessment of contributions of physicists Jagdish Chunder Bose and Karl Ferdinand Lindman to the development of artificial chiral media; Evaluation of developments in the field of engineered materials; Analysis of various aspects of double negative materials. [ABSTRACT FROM AUTHOR]

This paper develops a quasi-analytical and self-consistent model to compute the polarizabilities of split ring resonators (SRRs). An experimental setup is also proposed for measuring the magnetic polarizability of these structures. Experimental data are provided and compared with theoretical results computed following the proposed model. By using a local field approach, the model is applied to the obtaining of the dispersion characteristics of discrete negative magnetic permeability and left-handed metamaterials. Two types of SRRs, namely, the so-called edge coupled- and broadside Coupled- SRRs, have been considered. A comparative analysis of these two structures has been carried out in connection with their suitability for the design of metamaterials. Advantages and disadvantages of both structures are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we present an analysis for the radiation from a traveling-wave infinitely-extent sheet of monochromatic electric current that is placed at the interface between a conventional lossless dielectric and a lossless material possessing negative real permittivity and permeability. The field distributions and the direction of the Poynting vectors in both half spaces are discussed, and some physical remarks are provided. A brief note about launching Zenneck waves by a line current along this interface is also mentioned. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 460–463, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10638 [ABSTRACT FROM AUTHOR]

Abstract: Inspired by its analog from classic optics, we introduce one-atom-thick reflectors for infrared (IR) surface plasmon polaritons (SPP) surface waves based on graphene. Using numerical simulations, we first present the simple case of one-atom-thick straight-line mirror and then show how a one-atom-thick parabolic reflector (mirror) can be envisioned for focusing guided SPP waves on the graphene. [Copyright &y& Elsevier]

The article discusses the experimental progress in the electrodynamic properties and applied aspects of near-zero-index (NZI) media. It notes the exotic applications of NZI metamaterials, which typically a heterogeneous mixture with permittivity and permeability, and effective medium theories. It also discusses the possible use of photonic doping and single-inclusion metamaterials in controlling the scattering response of arbitrarily shaped body with a single and arbitrarily located actuator.