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The quest for invisibility has inspired a deep ardour in the research community over the past decade. The invention of metamaterials has boosted the research on electromagnetic cloaking due to its unusual electromagnetic parameters under plane wave incidence. In this study, we propose a novel cloaking scheme, using dogbone metamaterials, for effectively routing the incident electromagnetic fields around a target metal cylinder under consideration. Notable reduction in the scattered power is observed from the target in comparison to an uncloaked target. Experiments and simulations validate an effective reduction in the scattering cross section of the target and effective guiding of the incident plane wave around the target.

‘Nonlinear invisibility cloak’ using metamaterial is presented in this paper. To comprehend the said, the notion of point source, cylindrical source, perfect metamaterials and reduced metamaterials are taken for cloaking application. Transformation optics to the metamaterial envisages an interesting variation of both clocking shape and cloaking area with respect to aspect ratio. Simulation results revealed that both cloaking area and cloaking configuration are changed nonlinearly in case of (point source, exact metamaterial), (point source, reduced metamaterial), (cylindrical source, exact metamaterial) and (cylindrical source, reduced metamaterial).

We study the controversy about the proper determination of the electromagnetic energy-flux field in anisotropic materials, which has been revived due to the relatively recent experiments on negative refraction in metamaterials. Rather than analyzing energy-balance arguments, we use a pragmatic approach inspired by geometrical optics, and compare the predictions on angles of refraction at a flat interface of two possible choices on the energy flux: and . We carry out this comparison for a monochromatic Gaussian beam propagating in an anisotropic non-dissipative anisotropic metamaterial, in which the spatial localization of the electromagnetic field allows a more natural assignment of directions, in contrast to the usual study of plane waves. We compare our approach with the formalism of geometrical optics, which we generalize and analyze numerically the consequences of either choice.

Absorbers play an important role in protecting sensitive electronic devices from electromagnetic interference by absorbing the energy of incoming waves and reducing unnecessary reflection or transmission. In this paper we introduce new types of absorbers based on periodic structures, or the so-called metamaterials, which give us additional degrees of freedom to design the absorbing performance of absorbers with reduced thicknesses. Specifically, we demonstrate two types of metamaterial absorbers: one allowing us to customize absorption and other scattering parameters at selected frequencies; another absorbing only high-power microwaves and transmitting small signals even at the same frequency to maintain wireless communications. These metamaterial absorbers are expected to facilitate solving modern, complex EM interference issues where different-interdependent requirements exist.

Electromagnetic cloak is a device that has the potential to conceal an object by minimizing its total scattering cross section over a desired frequency. But due to causality constraints the material properties become dispersive which reduces cloaking bandwidth. In this work, the emphasis is on the study of various cloaking parameters like dispersive material properties, cloak dimensions, material losses which influence the real implementation of cloak. This work rigorously investigated the scattering performance at the design frequency and cloaking bandwidth for aforementioned parameters on the cloak design by utilizing a widely accepted term called total scattering cross section.

In this work, we investigate wave propagation through a zero index meta-material (ZIM) waveguide embedded with triangular dielectric defects. We provide a theoretical guidance on how to achieve total reflection and total transmission (i.e., cloaking) by adjusting the defect sizes and/or permittivities of the defects. Our work provides a systematical way in manipulating wave propagation through ZIM in addition to the widely studied dielectric defects with cylindrical and rectangular geometries.

We present spatial frequency maps of power flow in metamaterials and photonic crystals in order to provide insights into their electromagnetic responses and further our understanding of backward power in periodic structures. Since 2001, many different structures across the electromagnetic spectrum have been presented in the literature as exhibiting an isotropic negative effective index. Although these structures all exhibit circular or spherical equifrequency contours that resemble those of left-handed media, here we show through $k$-space diagrams that the distribution of power in the spatial frequency domain can vary considerably across these structures. In particular, we show that backward power arises from high-order right-handed harmonics in photonic crystals, magnetodielectric crystals, and across the layers of coupled-plasmonic-waveguide metamaterials, while arising from left-handed harmonic pairs in split-ring resonator and wire composites, plasmonic crystals, and along the layers of coupled-plasmonic-waveguide metamaterials. We also show that the fishnet structure exhibits the same left-handed harmonic pairs as the latter group. These observations allow us to categorize different metamaterials according to their spatial spectral source of backward power and identify the mechanism behind negative refraction at a given interface. Finally, we discuss how $k$-space maps of power flow can be used to explain the high or low transmittance of power into different metamaterial or photonic crystal structures.

Microwaves are not a simple heat source. Substances are heated directly by electromagnetic waves at energies commensurate with microwaves. Therefore, an understanding of the nature of these electromagnetic waves is the dominating discussion on microwave heating. Moreover, the coffee break continues the discussion regarding relationships between microwaves and foods, and the history of microwave cooking ovens. The chapter explains the basics of electromagnetic waves and how these electromagnetic waves are being used. Furthermore, the characteristics of microwaves in electromagnetic waves are clarified. The coffee break describes the use of microwaves at various frequencies.

Recently, metamaterials with near-zero refractive index have attracted much attention. Light inside these materials experiences no spatial phase change and extremely large phase velocity, makes these peculiar systems applicable for realizing directional emission, tunneling waveguides, large-area single-mode devices and electromagnetic cloaks. In addition, epsilon-near-zero (ENZ) metamaterials can also enhance light transmission through a subwavelength aperture. Impedance-matched all-dielectric zero-index metamaterials which exhibit Dirac cone dispersions at center of the Brillouin zone, have been experimentally demonstrated at microwave regime and optical frequencies for transverse-magnetic (TM) polarization of light. More recently, it has been also proved that these systems can be realized in a miniaturized in-plane geometry useful for integrated photonic applications, i.e. these metamaterials can be integrated with other optical elements, including waveguides, resonators and interferometers. In this work, using a zero-index metamaterial at the inner and outer sides of a subwavelength aperture, we numerically and experimental study light transmission through and its extraction from the aperture. The metamaterial consists of a combination of two double-layer arrays of scatterers with dissimilar subwavelength dimensions. The metamaterial exhibits zero-index optical response in microwave region. Our numerical investigation shows that the presence of the metamaterial at the inner side of the aperture leads to a considerable increase in the transmission of light through the subwavelength aperture. This enhancement is related to the amplification of the amplitude of the electromagnetic field inside the metamaterial which drastically increases the coupling between free space and the slit. By obtaining the electric field profile of the light passing through the considered NZI/aperture/NZI system at this frequency we found out that in addition to the enhanced transmission there is an excellent beaming of the extracted light from the structure. We have theoretically and experimentally shown that using a zero-index metamaterial at the inner and outer sides of a metallic subwavelength slit can considerably enhance the transmission of light through the aperture and beam its extraction, respectively. This work has been supported by TUBITAK under Project No 114E505. The author H.C. also acknowledges partial support from the Turkish Academy of Sciences.

Found an exact solution to the problem of electromagnetic radiation of a static charge, rotating at a constant speed. Expressions were obtained for the spectral components of the discrete spectrum of the radiation field frequencies in a «fixed» frame of reference. Shown the results of calculations for the case of the sub-light velocity of the charge. Analyzed elevation polarization characteristics and the dependence of the radiation spectrum on the velocity of the charge.

Transformation optics makes use of coordinate transformations to explore the possibilities offered by artificially structured metamaterials for the manipulation of a wide variety of electromagnetic phenomena. Since a decade, transformation optics has consistently extended its scope. Initially, coordinate transformations were only applied to the transformation of light in the simplest of optical setups, i.e., empty space [1,2]. In particular, straight light trajectories were being transformed into curved ones, e.g., avoiding a specific region in space (invisibility devices), bending over a specific angle (benders and splitters), and focussing to a particular point (lenses). Today, research efforts go beyond the transformation of empty space, allowing metamaterials to further enhance our control on electromagnetic phenomena other than light propagation. In this contribution, I will review our work on transformation optics to manipulate guided modes along and optical forces between metamaterial waveguides [3,4], the emission of Cerenkov radiation due to fast charged particles [5,6], and the Goos-Hanchen shift at metamaterial surfaces [7].

In this paper, metamaterials are regarded as a kind of specific medium. The application of three-dimensional electromagnetic field finite element mesh generation methods makes a finite element analysis and calculates the integral to metamaterials and its surrounding spatial structures so as to solve the spatial distribution of meta-materials and its surrounding electromagnetic parameter B and H under a certain frequency. In this way, the spatial distribution of the magnetic pole field in the metamaterials is obtained. Then, the process of making an integral treatment of it would give rise to the equivalent magnetic polarizability of the metamaterials.

Metamaterials have aroused tremendous interests in recent years owing to their peculiar electromagnetic (EM) properties and fascinating potential applications, e.g., invisibility cloak, perfect lens, etc.

In this letter, we present a nonlinear metamaterial capable of transitioning between a broadband reflective and broadband nonreflective state depending on the incident power level. Below the activation voltage, broadband reflectivity is created by forbidding propagation through the metamaterial as a result of the effective permittivity and permeability having different signs. Above the activation voltage, reflection is suppressed by matching the effective permittivity and permeability. Full-wave simulations are performed to analyze the electromagnetic characteristics of the structure, with experimental results presented at S-band frequencies in a WR-284 waveguide. These measurements demonstrate a 10 dB reduction in reflected amplitude over an 18% bandwidth, a 3-dB reduction over a greater than 30% bandwidth, and a maximum difference in reflection of nearly 42 dB.

Remarkable progress has been made over the past decade in controlling light propagation and absorption in compact devices using nanophotonic structures and metamaterials. From sensing and modulation, to on-chip communication and light trapping for solar cells, new device applications and opportunities motivate the need for a rigorous understanding of the modal properties of metamaterials over a broad range of frequencies. In this review, we provide an overview of a metamaterial band theory we have developed that rigorously models the behavior of metamaterials made of dispersive materials such as metals. The theory extends traditional photonic band theory for periodic dielectric structures by coupling the mechanical motion of electrons in the metal directly to Maxwell’s equations. The solution for the band structures of metamaterials is then reduced to a standard matrix eigenvalue problem that nevertheless fully takes into account the dispersive properties of the constituent materials. As an application of the metamaterial band theory, we show that one can develop a perturbation formalism based on this theory to physically explain and predict the effect of dielectric refractive index modulation or metallic plasma frequency variation in metamaterials. Furthermore, the metamaterial band theory also provides an intuitive physical picture of the source of modal material loss, as well as a rigorous upper bound on the modal material loss rate of any plasmonic, metamaterial structure. This in turn places fundamental limits on the broadband operation of such devices for applications such as photodetection and absorption.

Microwave metamaterials show promise in numerous low-power applications, ranging from strip lines to antennas. In general, metamaterials allow microwave designers to obtain electromagnetic characteristics not typically available in nature, leading to new behavior as well as reductions in the size of typical devices. High-power microwave (HPM) sources were efficient in the conventional microwave source community. We consider a specific use of metamaterials as a method to reduce the size of waveguide used for power transmission, particularly, a configuration in which an array of split-ring resonators (SRRs), forming a “mu-negative” structure, allows transmission of power in a waveguide well below the cutoff frequency. This configuration would not be used in an actual HPM device, but explores the methods and considerations that might be required for developing a metamaterial structure for either making HPM sources more compact or developing new types of interaction at these high powers. For any HPM application, a microwave structure must be able to sustain high electric and magnetic fields, as well as high peak and possibly average power. The challenge for metamaterials consists of devising the subwavelength structures (a defining characteristic of metamaterials) that can sustain such fields. In particular, one must understand the sensitivity of any metamaterial system to changes in the individual elements, which in high power pertains mainly to the loss of an individual resonator element. As such a sample system, we explore the physical operating characteristics of the waveguide system loaded with an array of SRRs, particularly the role of defects on its properties. Such defects would form an important feature in any high-power application in which subwavelength structures can be damaged by high field stresses.

We achieve strong local-field enhancement within a novel inhomogeneous metamaterial whose graded refractive index is realized using Dirac-cone metamaterials. This transition metamaterial provides a powerful tool for sensing, nonlinear optics, and quantum optics.

From the late 1700s through the 1800s there was intense activity and progress in defining the properties of electrostatic and electromagnetic forces, resulting in what is known as classical electrodynamics. These investigations would prove to be valuable prerequisites in later descriptions of the nature of light.

Transformation optics provides a geometry-based tool to create new components taking advantage of artificial metamaterials with optical properties that are not available in nature. Unfortunately, although guided electromagnetic waves are crucial for optical circuitry, transformation optics is not yet compatible with two-dimensional slab waveguides. Indeed, after determining the propagation of confined waves along the waveguide with a two-dimensional coordinate transformation, the conventional application of transformation optics results in metamaterials whose properties are insensitive to the coordinate perpendicular to the waveguide, leading to bulky, and therefore impractical, designs. In this contribution, we formulate an alternative framework that leads to feasible coordinate-based designs of two-dimensional waveguides. To this end, we characterize a guided transverse-magnetic light mode by relevant electromagnetic equations: a Helmholtz equation to account for wave propagation and a dispersion relation to impose a continuous light profile at the interface. By considering how two-dimensional conformal transformations transform these equations, we are able to materialize the coordinate-designed flows with a nonmagnetic metamaterial core of varying thickness, obtaining a two-dimensional device. We numerically demonstrate the effectiveness and versatility of our equivalence relations with three crucial functionalities, a beam bender, a beam splitter and a conformal lens, on a qualitative and quantitative level, by respectively comparing the electromagnetic fields inside and the transmission of our two-dimensional metamaterial devices to that of their three-dimensional counterparts at telecom wavelengths. As a result, we envision that one coordinate-based multifunctional waveguide component may seamlessly split and bend light beams on the landscape of an optical chip. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

While typically designed to manipulate classical light, metamaterials have many potential applications for quantum optics as well. We argue why a quantum optical effective-medium theory is needed. We present such a theory for layered metamaterials that is valid for light propagation in all spatial directions, thereby generalizing earlier work for one-dimensional propagation. In contrast to classical effective-medium theory there is an additional effective parameter that describes quantum noise. Our results for metamaterials are based on a rather general Lagrangian theory for the quantum electrodynamics of media with both loss and gain. In the second part of this paper, we present a new application of transformation optics whereby local spontaneous-emission rates of quantum emitters can be designed. This follows from an analysis how electromagnetic Green functions trans- form under coordinate transformations. Spontaneous-emission rates can be either enhanced or suppressed using invisibility cloaks or gradient index lenses. Furthermore, the anisotropic material profile of the cloak enables the directional control of spontaneous emission. MOE (Min. of Education, S’pore) Published version

A real-space gauge field provides an alternative way in bending light by shifting the local dispersion surfaces instead of changing their shapes or sizes in conventional gradient index media. Here, we show that such gauge field can be realized by anisotropic metamaterials. A metamaterial structure with balanced electric and magnetic responses is designed to materialize such gauge field. By combining with transformation optics, it allows us to design spin-dependent optical devices. A unidirectional retroreflector is demonstrated as an example.

In this talk, we present two experimental works on transformation optics and metamaterials in microwave frequency and electrostatics. The first is an experimental verification to an all-dielectric semi-spherical lens in the microwave regime, which exhibits extraordinary functions in shaping three-dimensional (3D) wave-propagation paths. On one hand, it was heuristically found that when radiation sources are placed in the central region, the lens behaves as a magnifying device, which resolves the sources in subwavelength scale. On the other hand, when impinging on the same semi-spherical lens from outside, the electromagnetic waves will be guided spirally inwards and absorbed efficiently by a normal absorber on the bottom surface. The 3D lens is composed of isotropic non-resonant metamaterials, which is fabricated by judiciously drilling inhomogeneous air holes in multi-layered dielectric plates. In electrostatics, the transformation optics will degenerate to transformation electrostatics. We present the concept of multi-functional transformation-dc devices, in which the functions of dc metamaterials can be remotely altered by illuminating visible light. We design, fabricate and test the anisotropic and inhomogeneous dc metamaterials using resistor network with light-sensitive semiconductor resistors embedded. When the illuminated light turns off, the dc device acts as an invisibility cloak; when we adjust the light power, the dc device exhibits various electrostatic illusions correspondingly. If the light-induced dc illusion effect is activated, the electrostatic behavior of the original object is perceived as multiple equivalent objects with different predesigned geometries. The experimental results of the functional device are in good agreement with the numerical simulations, which makes it possible to control the sophisticated passive transformation-dc devices using external light illuminations.

Conventional metamaterials are characterized by effective permittivity and permeability with continuous values. In analogy to the digital circuit that has only two distinct states ‘on’ and ‘off’, we proposed the concept of coding metamaterials, which is realized by distributing coding particles ‘0’ and ‘1’ with opposite reflection phases on a metasurface with a certain coding sequence. In this talk, we will introduce the concept of coding metamaterial, broadband diffusion of terahertz waves realized by the coding metamaterials, polarization-controlled anisotropic coding metamaterials, generation of single-beam THz radiations with arbitrary direction, and the information entropy of coding metasurfaces.

Electromagnetic metamaterials (MMs) consisting of highly conducting sub-wavelength metallic resonators enable many unusual electromagnetic properties at user defined frequencies which are not permissible with the naturally occurring materials [1, 2]. Generally the electromagnetic properties of metamaterials are controlled by the design variation of the MM unit cell, often termed as meta-molecule, consisting of single or multiple metallic split ring resonators (SRRs). These metallic resonators are quite often termed as meta-atoms too. The near field electromagnetic coupling between these meta-atoms exhibits an important role in modulating the fundamental resonances of the metamaterials [3–5].

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.

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.

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.

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.

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.

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

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.