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Metamaterials are artificial materials formed by highly subwavelength inclusions embedded in a host medium, which yield homogenized permittivity and permeability values. They offer electromagnetic unusual responses not generally available in nature. The aim of this paper is to provide a historical overview of electromagnetic (EM) metamaterials throughout last century, with the main focus on microwave and antennas applications.

In this paper, an analytical and numerical study of a new type of electromagnetic absorber, operating in the infrared and optical regime, is proposed. Absorption is obtained by exploiting Epsilon-Near-Zero materials. The structure electromagnetic properties are analytically described by using a new closed-form formula. In this way, it is possible to correlate the electromagnetic absorption properties of the structure with its geometrical characteristics. Good agreement between analytical and numerical results was achieved. Moreover, an absorption in a wide angle range (0°-80°), for different resonant frequencies (multi-band) with a large frequency bandwidth (wideband) for small structure thicknesses (d = λp/4) is obtained.

We review the connection between transmission-line metamaterials (TL-MTMs) and the transmission-line matrix (TLM) method for solving Maxwell's equations numerically. We show historically how the two disciplines evolved and how they are intimately related to each other We use the TLM method to reveal and explain the physics of the negative index property characterizing certain classes of transmission-line metamaterials as well as to inspire new research avenues in TL-MTMs.

In this paper, we experimentally validate the effects of different structures of metamaterial on efficiency enhancement in a four-coil magnetic resonant wireless power transfer system operating at 6.78MHz. First, we propose a concise design of magnetic metamaterials. A 6×6 planar array metamaterial slab is simulated to investigate its effect on power transmission between transmitter and receiver. The proposed metamaterials are fabricated for their application in the wireless power transfer system. Transmission and reflection coefficients of the system with 1-dimentional (including 1-slab and 2-slab), 2-dimentional, and 3-dimentional metamaterials at different positions are measured to investigate their influence on power transmission and to optimize the position of metamaterials in each case. Finally, the platform with metamaterials is utilized to light a 15W bulb to explicitly demonstrate the efficiency enhancement.

In this paper, an efficient magnetic resonance-based wireless power transfer (MRWPT) system with metamaterials is proposed. The negative permeability (MNG) metamaterials for this system with low-megahertz frequency is designed, which can be adjusted to work well at a variable receiving angle ranging from 0° to 45° along z-direction. The S-parameters, resonant frequency and permeability of metamaterials are computed for analysis. The transmission efficiency of the multiple-receiver MRWPT system in free space is compared to that in the presence of metamaterials placed in front of transmission and receive coils. The measured results show that the performance of the proposed metamaterials is perfect in improving the efficiency with incident electromagnetic waves from various directions.

The advent of metamaterials with tailorable frequency dispersion ensured the emergence of transformation optics with proposed applications that include cloaking devices, superconcentrators, superabsorbers, beam shapers and benders, field and polarization rotators, etc. A crucial property of interest for transformation optics is the possibility to custom design the spatial dependence of optical properties, i.e. to attain a gradient of effective refractive index. The cylindrical geometry has been one of the prototypal proposed forms and actually the first theoretical and experimental cloaking devices had radial symmetry. In this contribution we present an exact analytical approach to the solution of Helmholtz’ equations applied to radial propagation of electromagnetic waves through a cylinder containing negative and positive refractive index parts. A hyperbolic tangent gradient of refractive index is assumed. Our approach is inspired by the correspondence between transformation optics and quantum mechanics. A remarkably simple exact analytical solution is derived that takes into account realistic losses in negative-positive refractive index material composites.

Almost a decade ago, transformation optics established a geometrical perspective to describe the interaction of light with structured matter, enhancing our understanding and control of light. However, despite their huge technological relevance in applications such as optical circuitry, optical detection, and actuation, guided electromagnetic waves along dielectric waveguides have not yet benefited from the flexibility and conceptual simplicity of transformation optics. Indeed, transformation optics inherently imposes metamaterials not only inside the waveguide's core but also in the surrounding substrate and cladding. Here we restore the two-dimensional nature of guided electromagnetic waves by introducing a thickness variation on an anisotropic dielectric core according to alternative two-dimensional equivalence relations. Our waveguides require metamaterials only inside the core with the additional advantage that the metamaterials need not be magnetic and, hence, our purely dielectric waveguides are low loss. We verify the versatility of our theory with full wave simulations of three crucial functionalities: beam bending, beam splitting, and lensing. Our method opens up the toolbox of transformation optics to a plethora of waveguide-based devices.

Metamaterials with tunable negative permeability are proposed and investigated theoretically in this paper. First, the model of the dielectric bilayer sphere embedded in the dielectric substrate is put forward. Second, expressions of the electromagnetic fields in the model are derived based on the Mie scattering theory, and the general formula for the effective permeability of the model is deduced via the Maxwell-Garnett theory, which is further verified through the simulation results. Finally, the tunable bandwidth of the negative permeability of the metamaterials changing with the geometrical parameters is investigated based on the full-wave simulations, and the relative mechanisms are also discussed. It is believed that the results would be helpful for the practical applications of the metamaterials, and the metamaterials with tunable negative permeability proposed in the paper would facilitate the constructions of the left-handed materials in some degree.

We numerically and experimentally investigated the negative refractive index effect in a single subwavelength magnetic “meta-atom,” a flower-shaped metamaterial (MM) structure. In our effort to understand the electromagnetic properties of flower-shaped structure, the third resonance has been considered for a rather high frequency in the gigahertz range of electromagnetic wave. It is found that the negative refractive index is a result of the tail of electric gap and the magnetic resonance at the third-order resonance. The effect is switched OFF by adjusting the density of flowers. In addition, the negative refractive index behavior is accompanied by polarization insensitivity resulting from its geometry. Finally, the electromagnetic and the loss properties of the MM were clarified at the third-order gap.

The properties and applications of different types of ceramic all-dielectric metamaterials are presented. Metamaterials composed of arrays of identical ceramic resonators are shown to provide for negative refraction, enhanced transmission, and backward wave propagation. It is also demonstrated that arrays of dielectric elements can be used as non-resonant metamaterials to form a gradient index medium. Employment of such media in antenna substrates is shown perspective for antenna miniaturization without deteriorating antenna parameters. The development of a microwave transmission cloak composed of identical low-loss ceramic resonators to conceal object with the dimensions far exceeding the wavelength of incident radiation is also described.

Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. Then the relative photon-number densities of the transmitted field, the reflected field and the absorbed field are gotten through the correlation functions. Furthermore, the contributions of the relative permittivity and permeability of the metamaterials to the transmission are analyzed. Our results show that the permittivity and permeability reinforce the transmission for frequencies that are big compared with the magnetic resonance frequency.

Highly efficient and versatile computational electromagnetic analysis of 3-D transformation-based metamaterial cloaking structures based on a hybridization of a higher order finite element method for discretization of the cloaking region and a higher order method of moments for numerical termination of the computational domain is proposed and demonstrated. The technique allows for an effective modeling of the continuously inhomogeneous anisotropic cloaking region, for cloaks based on both linear and nonlinear coordinate transformations, using a very small number of large curved finite elements with continuous spatial variations of permittivity and permeability tensors and high-order p-refined field approximations throughout their volumes, with a very small total number of unknowns. In analysis, there is no need for a discretization of the permittivity and permeability profiles of the cloak, namely for piecewise homogeneous (layered) approximate models, with material tensors replaced by appropriate piecewise constant approximations. Numerical results show a very significant reduction (three to five orders of magnitude for the simplest possible 6-element model and five to seven orders of magnitude for an h-refined 24-element model) in the scattering cross section of a perfectly conducting sphere with a metamaterial cloak, in a broad range of wavelengths. Given the introduced explicit approximations in modeling of the spherical geometry and continuous material tensor profiles (both by fourth-order Lagrange interpolating functions), and inherent numerical approximations involved in the finite element and moment method techniques and codes, the cloaking effects are shown to be predicted rather accurately by the full-wave numerical analysis method.

Stealth technology in terms of absorption of electromagnetic waves is a most valuable research area for military purposes. Development of radar absorbing materials (RAM) had been actively researched for a quite long time. In the RAM design, weight, thickness, absorptivity, environmental resistance and mechanical strength are the key factors and therefore development of RAM with low density and high strength is a challenging task. As an alternative, research interest has shifted towards radar absorbing structures (RAS) and metamaterial is one of the lucrative options for the development of RAS. Metamaterials are a new class of ordered composites that exhibit exceptional electromagnetic properties not readily observed in nature. Built from microstructure that is small compared to wavelength of operation, metamaterials can be designed with effective permittivity and permeability values that can be large or small or even negative at any selected frequency. In this review paper, we first place the stealth technology in brief and then concept of metamaterials in context of conventional materials. We then discuss reflection theory of metamaterials from stealth point of view. Next section deals with recent progress towards its application as electromagnetic absorbers and future prospects especially in higher frequency region. Defence Science Journal, 2012, 62(4), pp.261-268 , DOI:http://dx.doi.org/10.14429/dsj.62.1514

In this article, we present a new theory to explain the phenomenon of negative refraction in bulk metamaterials. Unlike earlier theories, it does not rely on the existence of a single mode of propagation in materials with negative constitutive parameters. It is based on the interaction and phase reversal effects caused by the existence of two simultaneous electromagnetic (EM) modes in uniform inhomogeneous metamaterial structures. The theory is general in the sense that it may be applied with equal validity to quasilumped circuit-based microwave metamaterials and to optical negative refraction in bulk nanowire metamaterials. Validity of the theory is demonstrated with EM simulations of microwave and optical metamaterials.

A large scale homogenous invisibility cloak functioning at terahertz frequencies is reported. The terahertz invisibility device features a large concealed volume, low loss, and broad bandwidth. In particular, it is capable of hiding objects with a dimension nearly an order of magnitude larger than that of its lithographic counterpart, but without involving complex and time-consuming cleanroom processing.

We used newly developed experimental methods to collect educational video clips of electromagnetic waves propagating at the speed of light. The terahertz frequency waves were generated and detected in LiNbO3 crystals structured to reproduce classic optical geometries and experiments, such as two-slit interference and diffraction from a grating. Direct visualization of the phase fronts as the electromagnetic pulses propagate, reflect, diffract, and interfere helps develop intuition and understanding about the fundamental behavior of light and waves. We believe these videos will be a valuable addition to lectures on introductory optics and physics, because they bring contemporary research to the classroom and provide clear and direct experimental demonstrations of light and wave behavior.

Electromagnetic cloaking refers to the ability to prevent an object from scattering an incident electromagnetic field. This has been accomplished in recent works by specially designed materials. Another way of cloaking using sources has been known in the acoustics community. In this letter, we introduce a prescription for canceling the electromagnetic scattering of an object by using an array of sources. By using the equivalence principle, we show that by superimposing magnetic and electric surface current densities at the boundary of an object, the scattered fields from that object can be canceled. These magnetic and electric surface currents can be discretized into electric and magnetic dipoles that are physically implementable by straight and loop wire antennas. Finally, we confirm our results using numerical simulations.

The growing and rapid interest in new artificial metamaterials, whose properties differ from the normal materials has motivated further investigations. The metamaterials have simultaneously negative permittivity and permeability. In this work, we have demonstrated theoretically the existence and behavior of the TE guided waves in a ferromagnetic/metamaterial/antiferromagnetic waveguide structure. The dispersion characteristics are performed for different kinds of metamaterials. The existence and the type of the solutions to the guided waves with respect to different physical parameters are also investigated and discussed. It has been shown that the metamaterials can lead to different, new unusual properties.

Electromagnetic cloaking, or, in other words, techniques making objects “invisible” to the electromagnetic radiation, has attracted much attention in the last few years. Several different concepts have been proposed and studied analytically, numerically, and even experimentally. To make objects, especially strong scatterers, invisible to the impinging electromagnetic radiation is not an easy task. In this paper, we explain how the concept of transmission-line metamaterials, developed in the beginning of the 21st century, can be used in the creation of a special class of electromagnetic cloaking devices. We also make an overview of other approaches to electromagnetic cloaking.

The distribution of the electromagnetic field in a waveguide or slit is generally dependent on its shape and size. In this paper, we develop a general method to arbitrarily control the electromagnetic field through metamaterials, of which permittivity and/or permeability can be designed to continuously change from negative to positive values. With this method, the field distribution in a two-dimensional arbitrarily shaped waveguide or slit is totally dependent on the electromagnetic properties of metamaterials filled inside, but not on its shape or size. Permittivity and permeability of the metamaterials are derived, and transmission properties in the waveguide and slit are validated by numerical simulation. Results show that the field distribution inside the waveguide and slit can be easily controlled by the metamaterials. It provides a feasible way to control the electromagnetic field distribution.

The major issue regarding magnetic response in nature—“negative values for the permeability μ of material parameters, especially in terahertz or optical region” makes the electromagnetic properties of natural materials asymmetric. Recently, research in metamaterials has grown in significance because these artificial materials can demonstrate special and, indeed, extraordinary electromagnetic phenomena such as the inverse of Snell’s law and novel applications. A critical topic in metamaterials is the artificial negative magnetic response, which can be designed in the higher frequency regime (from microwave to optical range). Artificial magnetism illustrates new physics and new applications, which have been demonstrated over the past few years. In this review, we present recent developments in research on artificial magnetic metamaterials including split-ring resonator structures, sandwich structures, and high permittivity-based dielectric composites. Engineering applications such as invisibility cloaking, negative refractive index medium, and slowing light fall into this category. We also discuss the possibility that metamaterials can be suitable for realizing new and exotic electromagnetic properties.

In this chapter, we discuss some of the fundamentals of optics. We first cover the electromagnetic (EM) spectrum, which shows that the visible spectrum occupies just a very narrow portion of the entire EM spectrum. We then discuss geometrical optics and wave optics. In geometrical optics, we formulate the propagation of light rays in terms of matrices, whereas in wave optics we formulate wave propagation using the Fresnel diffraction formula, which is the solution to Maxwell’s equations. Fourier optics and its applications in optical image processing are then discussed. One of the important optical image processing applications in optical correlation is subsequently explained. Finally, we discuss the human visual system and end this chapter with a brief conclusion.

This paper proposes the study and implementation of metamaterials in electromagnetic non-destructive examination; these materials can serve as electromagnetic flux concentrators in the radio frequency range. Thus, the use of new types of metamaterials, namely conical Swiss roll, is proposed. Here, we present a method of extracting the necessary parameters (effective magnetic permeability and the frequency) from the data obtained by measuring network parameters. Due to the fact that conical Swiss rolls can serve as radio frequency flux concentrators, they can be used in the fabrication of electromagnetic lenses, being designed on the basis of Fourier optic principles. As a direct application, carbon fibre reinforced plastic (CFRP) plates with and without delaminations, created by impacts with low energy, were examined by means of electromagnetic transducers with a metamaterial lens. The characteristics of a carbon fibre woven structure become visible and the delaminations are clearly emphasised.

The majority of the designs of electromagnetic cloaks presented in the current literature require a metamaterial, the relative permittivity and/or permeability of which are smaller than one. Due to basic dispersion constraints, such permittivity (or permeability) can exist only within some restricted frequency band. This fact causes a passive electromagnetic cloak to be an inherently narrowband device. Here, it is shown both numerically and experimentally that the basic dispersion constraints of any passive medium might be overcome by using an active transmission line-based metamaterial. This type of metamaterial appears promising for the design of broadband cloaking devices.

We discuss methods for hiding of objects from detection by electromagnetic waves (cloaking), and also ways by which cloaked objects may be detected. The possibility of detection by means of thermal radiation emitted when electromagnetic energy is resonantly absorbed motivates the calculation of local density of states (LDOS), which controls the ability of a source inside a structured system to radiate. We give the first results of an investigation of the LDOS for systems which cloak by resonant interaction with electromagnetic fields. © 2010 Elsevier B.V.

Polarization is an important characteristic of electromagnetic (EM) waves, and efficient manipulations over EM wave polarizations are always desirable in practical applications. Here, we review the recent efforts in controlling light polarizations with metamaterials, at frequencies ranged from microwave to visible. We first presented a 4 × 4 version transfer matrix method (TMM) to study the scatterings by an anisotropic metamaterial of EM waves with arbitrary propagating directions and polarizations. With the 4 × 4 TMM, we discovered several amazing polarization manipulation phenomena based on the reflection geometry and proposed corresponding model metamaterial systems to realize such effects. Metamaterial samples were fabricated with the help of finite-difference-time-domain (FDTD) simulations, and experiments were performed to successfully realize these ideas at both microwave and visible frequencies. Efforts in employing metamaterials to manipulate light polarizations based on the transmission geometry are also reviewed.

We present the design, simulation, fabrication and characterization of structurally tunable metamaterials showing a marked tunability of the electric and magnetic responses at terahertz frequencies. Our results demonstrate that structurally tunable metamaterials offer significant potential to realize novel electromagnetic functionality ranging from dynamical filtering to reconfigurable cloaks or detectors. Furthermore, this approach is not limited to terahertz frequencies and may be readily used over much of the electromagnetic spectrum.

Underpinned by the advent of metamaterials, transformation optics offers great versatility for controlling electromagnetic waves to create materials with specially designed properties. Here we review the potential of transformation optics to create functionalities in which the optical properties can be designed almost at will. This approach can be used to engineer various optical illusion effects, such as the invisibility cloak.

Ray and caustic structures formed during propagation of electromagnetic waves from a point source of electromagnetic radiation in a layer of a metamaterial with a negative refractive index are studied. Propagation of waves in a homogeneous layer bounded by curvilinear surfaces with circular and parabolic shapes, i.e., in lenses of metamaterials, is analyzed. Propagation of waves in an inhomogeneous layer is considered in the cases of longitudinal and transverse variations in the refractive index. Caustic structures corresponding to wave catastrophes of caspoid and ombilic series are found. The possibility of backward waveguide propagation in a metamaterial is shown

We review some recent approaches to transmission enhancement and light harvesting based on optical nano-antennas and metamaterials. Nano-cavity antennas are used to enhance the extraordinary transmission of TM-polarized light through vertical nano-slits in a metal film. The enhanced transmission of TE-polarized waves through an array of subwavelength-slits in a thin metal film at low frequencies (including microwave) is also investigated. Light harvesting with a metamaterial cloaking shell is also demonstrated.

Electromagnetic cloaking has aroused increasing interest in the scientific community, especially amongst researchers who are developing so-called metamaterials - artificial composites having exotic electromagnetic properties. In this paper we review the basic principles of metamaterials, especially those for cloaking applications, and describe the recent developments in the field of electromagnetic cloaking. Attention is given also to the recently proposed cloaking technique which is based on networks of transmission lines.

Metamaterials are understood to be artificially engineered materials that exhibit unusual or difficult to obtain electromagnetic (EM) properties. Such properties would include negative or low values of permittivity, permeability and index of refraction. In this article, we review the fundamentals of metamaterials with emphasis on negative-refractive-index ones, which are synthesized using loaded transmission lines. A number of applications of such metamaterials are discussed, including peculiar lenses that can overcome the diffraction limit and small antennas for emerging wireless communication applications.

In coordinate-transformation-based approaches to electromagnetic concealment (“cloaking”) of objects, use of higher-order (quadratic) mappings has been proposed as an effective device to obtain satisfactory responses without the use of magnetic materials that are complicated to synthesize at optical frequencies. In this article, we explore a new higher-order algebraic transformation, which allows, in principle, for a broader range of applicability and further parametric optimization. Via full-wave numerical studies of near- and far-field observables, we assess its performance by comparison with various reference cases (nonreduced parameters, quadratic transformation, no cloak). © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3186–3190, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23905

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.

Metamaterials, which were discussed at a meeting of the RAS Presidium, are artificially produced or composed media whose properties are determined by parameters of their elements and may be very unusual. Some metamaterials refract or reflect electromagnetic waves (light) in a way that is not available in nature. Others, such as photonic crystals, can stop (lock) electromagnetic waves or transmit them along channels (waveguides) that normally do not propagate such waves. The unique properties of metamaterials and their possible applications are discussed in the article below.

It is known that the spectrum of light can change on propagation, even in free space. Such changes are due to its coherence properties. We determine how the spectrum of a stochastic electromagnetic beam of any state of coherence changes on propagation in atmospheric turbulence. We illustrate the results by examining changes in the spectrum of an electromagnetic Gaussian Schell-model beam whose spectrum consists of a single spectral line with a Gaussian profile, which propagates through atmospheric turbulence, with Kolmogorov power spectrum. The results are of interest for optical communications through the atmosphere and for laser radar systems.

The idea behind invisibility is to make light travel around an object in the same time that it would take it to go in a straight line if the object was not there. To achieve this, the object must be surrounded by a material that can propagate light at a speed faster than in a vacuum. Metamaterials, where the structure as well as the chemistry influences the optical properties, have been known for a long time. Metamaterials with a negative refractive index already been produced by bending the light in the opposite way from the expected one - the sort of approach required to make sure that something cannot be seen. Metamaterials work by resonance at a given frequency (related to the wavelength) and will only resonate perfectly at that very frequency. Because the range for visible light is so broad, people predict that current approaches would only make an object invisible at a particular colour.

In this review we describe the challenges and opportunities for creating magnetically active metamaterials in the optical part of the spectrum. The emphasis is on the sub-wavelength periodic metamaterials whose unit cell is much smaller than the optical wavelength. The conceptual differences between microwave and optical metamaterials are demonstrated. We also describe several theoretical techniques used for calculating the effective parameters of plasmonic metamaterials: the effective dielectric permittivity eff(!) and magnetic permeability µeff(!). Several examples of negative permittivity and negative permeability plasmonic metamaterials are used to illustrate the theory.

Metamaterials exhibit numerous novel effects1,2,3,4,5 and operate over a large portion of the electromagnetic spectrum6,7,8,9,10. Metamaterial devices based on these effects include gradient-index lenses11,12, modulators for terahertz radiation13,14,15 and compact waveguides16. The resonant nature of metamaterials results in frequency dispersion and narrow bandwidth operation where the centre frequency is fixed by the geometry and dimensions of the elements comprising the metamaterial composite. The creation of frequency-agile metamaterials would extend the spectral range over which devices function and, further, enable the manufacture of new devices such as dynamically tunable notch filters. Here, we demonstrate such frequency-agile metamaterials operating in the far-infrared by incorporating semiconductors in critical regions of metallic split-ring resonators. For this first-generation device, external optical control results in tuning of the metamaterial resonance frequency by ∼20%. Our approach is integrable with current semiconductor technologies and can be implemented in other regions of the electromagnetic spectrum. Metamaterials that possess frequency tunability enable new device functions. By external optical control through the incorporation of semiconductors in metallic split-ring resonators, the researchers provide an elegant solution to frequency-agile terahertz metamaterials.

Features of spatial power spectrum (SPS) of scattered radiation in a randomly inhomogeneous medium with strongly prolated anisotropic inhomogeneities of dielectric permittivity are investigated. In single scattering approximation, it has been shown that a pronounced gap along a direction of prolate inhomogeneities appears in SPS. Features of SPS of multiple scattered waves at oblique illumination of a boundary of randomly-inhomogeneous medium with prolate irregularities have been analytically studied using smooth perturbation method taking into account diffraction effects. Numerical calculations have shown that with an increase of a distance passing by 192 Gavrilenko et al. the wave in random media, SPS has a double-peaked shape and a gap substantially increases. Its maximum is slightly changed and the width is broadening. The results have been obtained analytically for the first time and could find extensive practical application in optics and be useful in development of principles of remote sensing of random media.

The exciting field of metamaterials has attracted the interest of researchers from all across the world over the past few years. With roots in the foundations of optics and electromagnetics, researchers are exploring the underlying physics of metamaterials. Electromagnetic metamaterials are artificially structured materials composed of periodic arrays of sub-wavelength resonating structures, scatterers or apertures, whose electric or magnetic response provides the ability to engineer dielectric or magnetic properties that do not exist in naturally occurring materials. The dielectric or magnetic properties can be tailored by changing the geometrical parameters of the constituent structure of the metamaterial.

Maxwell’s equations constitute the basis of optics and electromagnetic theory, where these equations may be considered from the classical or the quantum point of view. Basic ideas and relations in the classical electromagnetic theory are briefly reviewed in this chapter. Important features of the monochromatic plane wave are indicated, including reflection, refraction, and total internal reflection at a planar interface. Features of plane wave propagation in dispersive dielectrics and conducting media are outlined. The relation between group velocity, velocity of energy propagation, and signal velocity is elucidated, referring to Sommerfeld’s and Brillouin’s work. It is briefly explained why a superluminal group velocity does not imply a violation of causality. Spherical and cylindrical wave solutions of Maxwell’s equations are introduced. Features of plane wave propagation in anisotropic media are discussed. Wave propagation in artificially engineered metamaterials is explained in outline. Basic concepts relating to coherence and states of polarization of electromagnetic waves are introduced.

Manipulation of radiation is required for enabling a span of electromagnetic applications. Since properties of antennas and scatterers are very sensitive to the surrounding environment, macroscopic artificially created materials are good candidates for shaping their characteristics. In particular, metamaterials enable controlling both dispersion and density of electromagnetic states, available for scattering from an object. As a result, properly designed electromagnetic environments could govern wave phenomena and tailor various characteristics. Here electromagnetic properties of scattering dipoles, situated inside a wire medium (metamaterial), are analyzed both numerically and experimentally. The effect of the metamaterial geometry, dipole arrangement inside the medium, and frequency of the incident radiation on the scattering phenomena is studied in detail. It is shown that the resonance of the dipole hybridizes with Fabry-Perot modes of the metamaterial, giving rise to a complete reshaping of electromagnetic properties. Regimes of controlled scattering suppression and super-scattering are experimentally observed. Numerical analysis is in agreement with the experiment, performed at the GHz spectral range. The reported approach to scattering control with metamaterials could be directly mapped into optical and infrared spectral ranges by employing scalability properties of Maxwell's equations.

An optical metamaterial is a composite in which subwavelength features, rather than the constituent materials, control the macroscopic electromagnetic properties of the material. Recently, properly designed metamaterials have garnered much interest because of their unusual interaction with electromagnetic waves. Whereas nature seems to have limits on the type of materials that exist, newly invented metamaterials are not bound by such constraints. These newly accessible electromagnetic properties make these materials an excellent platform for demonstrating unusual optical phenomena and unique applications such as subwavelength imaging and planar lens design. 'Negative-index materials', as first proposed, required the permittivity, epsilon, and permeability, mu, to be simultaneously less than zero, but such materials face limitations. Here, we demonstrate a comparatively low-loss, three-dimensional, all-semiconductor metamaterial that exhibits negative refraction for all incidence angles in the long-wave infrared region and requires only an anisotropic dielectric function with a single resonance. Using reflection and transmission measurements and a comprehensive model of the material, we demonstrate that our material exhibits negative refraction. This is furthermore confirmed through a straightforward beam optics experiment. This work will influence future metamaterial designs and their incorporation into optical semiconductor devices.

Planar electric metamaterials are experimentally studied in transmission and reflection utilizing terahertz time-domain spectroscopy. Electrically resonant behavior is observed and provides an estimate of the frequency-dependent transmissivity, reflectivity, and absorptivity of metamaterial composites. Numerical simulations are in good agreement with the measured results and provide additional information helpful in understanding their electromagnetic response. Our results and approach help define the boundaries of a metamaterials-based design paradigm and should prove beneficial in future terahertz applications, particularly with respect to novel filtering, modulation, and switching devices. In addition, this work clarifies some of the mechanisms that limit efficient metamaterials operation at higher-frequencies.

In this letter, we find that gradient index metamaterials (GIMs) could be utilized to manipulate wave propagation in waveguides. Through manipulating the conversion between propagating wave and surface wave, we can design some interesting applications in waveguides, such as controlling transmission effect, realizing bending waveguide and achieving waveguide splitting effect. These devices not only work for both transverse electric and magnetic polarized waves, but also function for a broadband of spectra. Numerical simulations are performed to verify our findings.

In this review article, a brief introduction on the theory, experiments and applications of metamaterials is presented. The main focuses are concentrated on the composing meta-atoms, the method of transformation optics, the experimental demonstration of negative refraction, and the realizations of invisibility cloaks and electromagnetic black hole. At the end of this review, some typical applications of metamaterials, including high-performance antennas made of zero-refractive-index materials, inhomogeneous metamaterial lenses, and planar metasurfaces, are introduced in details.

In this paper, a metamaterial based triangular shaped electromagnetic cloak is presented. The pi-shaped metamaterial shows wideband NZRI (near-zero refractive-index) characteristics in the C-band of microwave spectra. The metamaterial was then utilized in designing a triangular shaped cloak. The cloak hides a metal cylinder electromagnetically where the metamaterial shows NZRI property. At the cloaked frequency, the normalized scattering width (NSW) of the object was reduced to zero. This is a promising design for wideband NZRI characteristics and C-band electromagnetic cloaking operation.