Showing papers on "Metamaterial published in 2006"

Metamaterial Electromagnetic Cloak at Microwave Frequencies

Abstract: A recently published theory has suggested that a cloak of invisibility is in principle possible, at least over a narrow frequency band. We describe here the first practical realization of such a cloak; in our demonstration, a copper cylinder was "hidden" inside a cloak constructed according to the previous theoretical prescription. The cloak was constructed with the use of artificially structured metamaterials, designed for operation over a band of microwave frequencies. The cloak decreased scattering from the hidden object while at the same time reducing its shadow, so that the cloak and object combined began to resemble empty space.

Optical Conformal Mapping

Abstract: An invisibility device should guide light around an object as if nothing were there, regardless of where the light comes from. Ideal invisibility devices are impossible, owing to the wave nature of light. This study develops a general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics. The imperfections of invisibility can be made arbitrarily small to hide objects that are much larger than the wavelength. With the use of modern metamaterials, practical demonstrations of such devices may be possible. The method developed here can also be applied to escape detection by other electromagnetic waves or sound.

Structural diversity in binary nanoparticle superlattices

Abstract: The assembly of nanoparticles of two different materials into a binary nanoparticle superlattice is a promising way of synthesizing a large variety of materials (metamaterials) with precisely controlled chemical composition and tight placement of the components. In theory only a few stable binary superlattice structures can assemble from hard spheres, potentially limiting this approach. But all is not lost because at the nanometre scale there are additional forces (electrostatic, van der Waals and dipolar) that can stabilize binary nanoparticulate structures. Shevchenko et al. now report the synthesis of a dozen novel structures from various combinations of metal, semiconductor, magnetic and dielectric nanoparticles. This demonstrates the potential of self-assembly in designing families of novel materials and metamaterials with programmable physical and chemical properties. Assembly of small building blocks such as atoms, molecules and nanoparticles into macroscopic structures—that is, ‘bottom up’ assembly—is a theme that runs through chemistry, biology and material science. Bacteria1, macromolecules2 and nanoparticles3 can self-assemble, generating ordered structures with a precision that challenges current lithographic techniques. The assembly of nanoparticles of two different materials into a binary nanoparticle superlattice (BNSL)3,4,5,6,7 can provide a general and inexpensive path to a large variety of materials (metamaterials) with precisely controlled chemical composition and tight placement of the components. Maximization of the nanoparticle packing density has been proposed as the driving force for BNSL formation3,8,9, and only a few BNSL structures have been predicted to be thermodynamically stable. Recently, colloidal crystals with micrometre-scale lattice spacings have been grown from oppositely charged polymethyl methacrylate spheres10,11. Here we demonstrate formation of more than 15 different BNSL structures, using combinations of semiconducting, metallic and magnetic nanoparticle building blocks. At least ten of these colloidal crystalline structures have not been reported previously. We demonstrate that electrical charges on sterically stabilized nanoparticles determine BNSL stoichiometry; additional contributions from entropic, van der Waals, steric and dipolar forces stabilize the variety of BNSL structures.

Ultrasonic metamaterials with negative modulus

Abstract: The emergence of artificially designed subwavelength electromagnetic materials, denoted metamaterials, has significantly broadened the range of material responses found in nature. However, the acoustic analogue to electromagnetic metamaterials has, so far, not been investigated. We report a new class of ultrasonic metamaterials consisting of an array of subwavelength Helmholtz resonators with designed acoustic inductance and capacitance. These materials have an effective dynamic modulus with negative values near the resonance frequency. As a result, these ultrasonic metamaterials can convey acoustic waves with a group velocity antiparallel to phase velocity, as observed experimentally. On the basis of homogenized-media theory, we calculated the dispersion and transmission, which agrees well with experiments near 30 kHz. As the negative dynamic modulus leads to a richness of surface states with very large wavevectors, this new class of acoustic metamaterials may offer interesting applications, such as acoustic negative refraction and superlensing below the diffraction limit.

Metamaterials: Physics and Engineering Explorations

Abstract: Preface. Contributors. PART I: DOUBLE-NEGATIVE (DNG) METAMATERIALS. SECTION I: THREE-DIMENSIONAL VOLUMETRIC DNG METAMATERIALS. CHAPTER 1: INTRODUCTION, HISTORY, AND SELECTED TOPICS IN FUNDAMENTAL THEORIES OF METAMATERIALS (Richard W. Ziolkowski and Nader Engheta). 1.1 Introduction. 1.2 Wave Parameters in DNG Media. 1.3 FDTD Simulations of DNG Media. 1.4 Causality in DNG Media. 1.5 Scattering from a DNG Slab. 1.6 Backward Waves. 1.7 Negative Refraction. 1.8 Phase Compensation with a DNG Medium. 1.9 Dispersion Compensation in a Transmission Line Using a DNG Medium. 1.10 Subwavelength Focusing with a DNG Medium. 1.11 Metamaterials with a Zero Index of Refraction. 1.12 Summary. References. CHAPTER 2: FUNDAMENTALS OF WAVEGUIDE AND ANTENNA APPLICATIONS INVOLVING DNG AND SNG METAMATERIALS (Nader Engheta, Andrea Alu, Richard W. Ziolkowski, and Aycan Erentok). 2.1 Introduction. 2.2 Subwavelength Cavities and Waveguides. 2.3 Subwavelength Cylindrical and Spherical Core-Shell Systems. 2.4 ENG-MNG and DPS-DNG Matched Metamaterial Pairs for Resonant Enhancements of Source-Generated Fields. 2.5 Efficient, Electrically Small Dipole Antennas: DNG Nested Shells. 2.6 Efficient, Electrically Small Dipole Antennas: ENG Nested Shells-Analysis. 2.7 Efficient, Electrically Small Dipole Antennas: HFSS Simulations of Dipole-ENG Shell Systems. 2.8 Metamaterial Realization of an Artificial Magnetic Conductor for Antenna Applications. 2.9 Zero-Index Metamaterials for Antenna Applications. 2.10 Summary. References. CHAPTER 3: WAVEGUIDE EXPERIMENTS TO CHARACTERIZE PROPERTIES OF SNG AND DNG METAMATERIALS (Silvio Hrabar). 3.1 Introduction. 3.2 Basic Types of Bulk Metamaterials with Inclusions. 3.3 Theoretical Analysis of Rectangular Waveguide Filled with General Metamaterial. 3.4 Investigation of Rectangular Waveguide Filled with 2D Isotropic ENG Metamaterial. 3.5 Investigation of Rectangular Waveguide Filled with 2D Isotropic MNG Metamaterial. 3.6 Investigation of Rectangular Waveguide Filled with 2D Uniaxial MNG Metamaterial. 3.7 Investigation of Rectangular Waveguide Filled with 2D Isotropic DNG Metamaterial. 3.8 Investigation of Subwavelength Resonator. 3.9 Conclusions. References. CHAPTER 4: REFRACTION EXPERIMENTS IN WAVEGUIDE ENVIRONMENTS (Tomasz M. Grzegorczyk, Jin Au Kong, and Ran Lixin). 4.1 Introduction. 4.2 Microscopic and Macroscopic Views of Metamaterials. 4.3 Measurement Techniques. 4.4 Conclusion. Acknowledgments. References. SECTION II: TWO-DIMENSIONAL PLANAR NEGATIVE-INDEX STRUCTURES. CHAPTER 5: ANTENNA APPLICATIONS AND SUBWAVELENGTH FOCUSING USING NEGATIVE-REFRACTIVE-INDEX TRANSMISSION LINE STRUCTURES (George V. Eleftheriades). 5.1 Introduction. 5.2 Planar Transmission Line Media with Negative Refractive Index. 5.3 Zero-Degree Phase-Shifting Lines and Applications. 5.4 Backward Leaky-Wave Antenna Radiating in Its Fundamental Spatial Harmonic. 5.5 Superresolving NRI Transmission Line Lens. 5.6 Detailed Dispersion of Planar NRI-TL Media. Acknowledgments. References. CHAPTER 6: RESONANCE CONE ANTENNAS (Keith G. Balmain and Andrea A. E. Luttgen). 6.1 Introduction. 6.2 Planar Metamaterial, Corner-Fed, Anisotropic Grid Antenna. 6.3 Resonance Cone Refraction Effects in a Low-Profile Antenna. 6.4 Conclusions. Acknowledgments. References. CHAPTER 7: MICROWAVE COUPLER AND RESONATOR APPLICATIONS OF NRI PLANAR STRUCTURES (Christophe Caloz and Tatsuo Itoh). 7.1 Introduction. 7.2 Composite Right/Left-Handed Transmission Line Metamaterials. 7.3 Metamaterial Couplers. 7.4 Metamaterial Resonators. 7.5 Conclusions. References. PART II: ELECTROMAGNETIC BANDGAP (EBG) METAMATERIALS. SECTION I: THREE-DIMENSIONAL VOLUMETRIC EBG MEDIA. CHAPTER 8: HISTORICAL PERSPECTIVE AND REVIEW OF FUNDAMENTAL PRINCIPLES IN MODELING THREE-DIMENSIONAL PERIODIC STRUCTURES WITH EMPHASIS ON VOLUMETRIC EBGs (Maria Kafesaki and Costas M. Soukoulis). 8.1 Introduction. 8.2 Theoretical and Numerical Methods. 8.3 Comparison of Different Numerical Techniques. 8.4 Conclusions. Acknowledgments. References. CHAPTER 9: FABRICATION, EXPERIMENTATION, AND APPLICATIONS OF EBG STRUCTURES (Peter de Maagt and Peter Huggard). 9.1 Introduction. 9.2 Manufacturing. 9.3 Experimental Characterization of EBG Crystals. 9.4 Current and Future Applications of EBG Systems. 9.5 Conclusions. References. CHAPTER 10: SUPERPRISM EFFECTS AND EBG ANTENNA APPLICATIONS (Boris Gralak, Stefan Enoch, and G-erard Tayeb). 10.1 Introduction. 10.2 Refractive Properties of a Piece of Photonic Crystal. 10.3 Superprism Effect. 10.4 Antenna Applications. 10.5 Conclusion. References. SECTION II: TWO-DIMENSIONAL PLANAR EBG STRUCTURES. CHAPTER 11: REVIEW OF THEORY, FABRICATION, AND APPLICATIONS OF HIGH-IMPEDANCE GROUND PLANES (Dan Sievenpiper). 11.1 Introduction. 11.2 Surface Waves. 11.3 High-Impedance Surfaces. 11.4 Surface Wave Bands. 11.5 Reflection Phase. 11.6 Bandwidth. 11.7 Design Procedure. 11.8 Antenna Applications. 11.9 Tunable Impedance Surfaces. 11.10 Reflective-Beam Steering. 11.11 Leaky-Wave Beam Steering. 11.12 Backward Bands. 11.13 Summary. References. CHAPTER 12: DEVELOPMENT OF COMPLEX ARTIFICIAL GROUND PLANES IN ANTENNA ENGINEERING (Yahya Rahmat-Samii and Fan Yang). 12.1 Introduction. 12.2 FDTD Analysis of Complex Artificial Ground Planes. 12.3 Various Complex Artificial Ground-Plane Designs. 12.4 Applications of Artificial Ground Planes in Antenna Engineering. 12.5 Summary. References. CHAPTER 13: FSS-BASED EBG SURFACES (Stefano Maci and Alessio Cucini). 13.1 Introduction. 13.2 MoM Solution. 13.3 Accessible Mode Admittance Network. 13.4 Pole-Zero Matching Method for Dispersion Analysis. 13.5 Conclusions. Acknowledgments. References. CHAPTER 14: SPACE-FILLING CURVE HIGH-IMPEDANCE GROUND PLANES (John McVay, Nader Engheta, and Ahmad Hoorfar). 14.1 Resonances of Space-Filling Curve Elements. 14.2 High-Impedance Surfaces Made of Space-Filling Curve Inclusions. 14.3 Use of Space-Filling Curve High-Impedance Surfaces in Antenna Applications. 14.4 Space-Filling Curve Elements as Inclusions in DNG Bulk Media. 14.5 Conclusions. References. Index.

Optical Hyperlens: Far-field imaging beyond the diffraction limit.

Abstract: We propose an approach to far-field optical imaging beyond the diffraction limit. The proposed system allows image magnification, is robust with respect to material losses and can be fabricated by adapting existing metamaterial technologies in a cylindrical geometry.

Tunneling of electromagnetic energy through subwavelength channels and bends using ε-near-zero materials

Abstract: In this Letter, we demonstrate theoretically that electromagnetic waves can be ``squeezed'' and tunneled through very narrow channels filled with $\ensuremath{\epsilon}$-near-zero (ENZ) materials. We show that the incoming planar wave front is replicated at the output interface, independently of the specific geometry of the channel. A closed analytical formula is derived for the scattering parameters of a particular class of geometries. It is discussed that in some cases the isotropy of the ENZ material may not be an issue. A metamaterial realization of an anisotropic ENZ material is suggested and numerically studied.

Simultaneous Negative Phase and Group Velocity of Light in a Metamaterial

Abstract: We investigated the propagation of femtosecond laser pulses through a metamaterial that has a negative index of refraction for wavelengths around 1.5 micrometers. From the interference fringes of a Michelson interferometer with and without the sample, we directly inferred the phase time delay. From the pulse-envelope shift, we determined the group time delay. In a spectral region, phase and group velocity are negative simultaneously. This means that both the carrier wave and the pulse envelope peak of the output pulse appear at the rear side of the sample before their input pulse counterparts have entered the front side of the sample.

Electric-field-coupled resonators for negative permittivity metamaterials

Abstract: A lithographically patterned inductive-capacitive resonator is described that has a strong electric response. This resonator can be used to construct metamaterials with desired positive or negative permittivity. Such materials provide an alternative to wire media, and have the benefit of not requiring continuous current paths between unit cells. A planar medium composed of these resonators was simulated, fabricated, and measured in the microwave frequency range.

Far-field subdiffraction optical microscopy using metamaterial crystals: Theory and simulations

Abstract: Here we suggest and explore theoretically an idea for a far-field scanless optical microscopy with a subdiffraction resolution. We exploit the special dispersion characteristics of an anisotropic metamaterial crystal that is obliquely cut at its output plane, or has a curved output surface, in order to map the input field distribution onto the crystal's output surface with a compressed angular spectrum, resulting in a ``magnified'' image. This can provide a far-field imaging system with a resolution beyond the diffraction limits while no scanning is needed.

Second-harmonic generation from magnetic metamaterials.

Abstract: We observe second-harmonic generation from metamaterials composed of split-ring resonators excited at 1.5-micrometer wavelength. Much larger signals are detected when magnetic-dipole resonances are excited, as compared with purely electric-dipole resonances. The experiments are consistent with calculations based on the magnetic component of the Lorentz force exerted on metal electrons-an intrinsic second-harmonic generation mechanism that plays no role in natural materials. This unusual mechanism becomes relevant in our work as a result of the enhancement and the orientation of the local magnetic fields associated with the magnetic-dipole resonances of the split-ring resonators.

General relativity in electrical engineering

Abstract: In electrical engineering metamaterials have been developed that offer unprecedented control over electromagnetic fields. Here, we show that general relativity provides the theoretical tools for designing devices made of such versatile materials. Given a desired device function, the theory describes the electromagnetic properties that turn this function into fact. We consider media that facilitate space-time transformations and include negative refraction. Our theory unifies the concepts operating behind the scenes of perfect invisibility devices, perfect lenses, the optical Aharonov–Bohm effect and electromagnetic analogues of the event horizon, and may lead to further applications.

Homogenization of metamaterials by field averaging (invited paper)

Abstract: Over the past several years, metamaterials have been introduced and rapidly been adopted as a means of achieving unique electromagnetic material response. In metamaterials, artificially structured—often periodically positioned—inclusions replace the atoms and molecules of conventional materials. The scale of these inclusions is smaller than that of the electromagnetic wavelength of interest, so that a homogenized description applies. We present a homogenization technique in which macroscopic fields are determined via averaging the local fields obtained from a full-wave electromagnetic simulation or analytical calculation. The field-averaging method can be applied to homogenize any periodic structure with unit cells having inclusions of arbitrary geometry and material. By analyzing the dispersion diagrams and retrieved parameters found by field averaging, we review the properties of several basic metamaterial structures. © 2006 Optical Society of America OCIS codes: 160.0160, 160.1190, 260.2110, 350.5500.

Directed subwavelength imaging using a layered metal-dielectric system

Abstract: We examine some of the optical properties of a metamaterial consisting of thin layers of alternating metal and dielectric. We can model this material as a homogeneous effective medium with anisotropic dielectric permittivity. When the components of this permittivity have different signs, the behavior of the system becomes very interesting: the normally evanescent parts of a $P$-polarized incident field are now transmitted, and there is a preferred direction of propagation. We show that a slab of this material can form an image with subwavelength details, at a position which depends on the frequency of light used. The quality of the image is affected by absorption and by the finite width of the layers; we go beyond the effective-medium approximation to predict how thin the layers need to be in order to obtain subwavelength resolution.

Metamaterial-based efficient electrically small antennas

Abstract: A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane Analytical and numerical models demonstrate that a properly designed ENG shell provides a distributed inductive element resonantly matched to these highly capacitive electrically small antennas, ie, an ENG shell can be designed to produce an electrically small system with a zero input reactance and an input resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity Losses and dispersion characteristics of the ENG materials are also included in the analytical models Finite element numerical models of the various antenna-ENG shell systems are developed and used to predict their input impedances These electrically small antenna-ENG shell systems with idealized dispersionless ENG material properties are shown to be very efficient and to have fractional bandwidths above the values associated with the Chu limit for the quality factor without any degradation in the radiation patterns of the antennas Introducing dispersion and losses into the analytical models, the resulting bandwidths are shown to be reduced significantly, but remain slightly above (below) the corresponding Chu-based value for an energy-based limiting (Drude) dispersion model of the permittivity of the ENG shell

Low-loss negative-index metamaterial at telecommunication wavelengths

Abstract: We fabricate and characterize a low-loss silver-based negative-index metamaterial based on the design of a recent theoretical proposal. Comparing the measured transmittance and reflectance spectra with theory reveals good agreement. We retrieve a real part of the refractive index of Re(n)= -2 around 1.5 microm wavelength. The maximum of the ratio of the real to the imaginary part of the refractive index is about three at a spectral position where Re(n)= -1. To the best of our knowledge, this is the best figure of merit reported for any negative-index photonic metamaterial to date.

A substrate for small patch antennas providing tunable miniaturization factors

Abstract: Magnetic properties were imparted to a naturally nonmagnetic material by metallic inclusions. A patch antenna tested the performance of the magnetic metamaterial as a substrate and validated that a single substrate can achieve a range of miniaturization values. The effective medium metamaterial substrate employed electromagnetically small embedded circuits (ECs) to achieve permeability and permittivity greater than that of the host dielectric. Geometric control of the ECs allowed mu and epsi to be tailored to the application. The magnetic metamaterial exhibited enhanced mu and epsi with acceptable loss-factor levels. Models for predicting mu and epsi are presented, the benefits of employing metamaterial substrates are discussed, and the results in this antenna experiment are presented. The metamaterial exhibits performance characteristics not achievable from natural materials. Of particular significance is that with the permeability varying strongly and predictably with frequency, the miniaturization factor may be selected by tuning the operating frequency. Simulations indicate that such performance can be extended to several gigahertz with current technology. Relative permeability values in the mur=1-5 range are achievable for moderately low-loss applications. Representative antenna miniaturization factors on the order of 4-7 over a moderate (approximately 10%) transmission bandwidth and efficiencies in a moderate range (20%-35%) are demonstrated with the possibility of higher efficiencies indicated

Negative effective permeability and left-handed materials at optical frequencies.

Abstract: We present here the design of nano-inclusions made of properly arranged collections of plasmonic metallic nano-particles that may exhibit a resonant magnetic dipole collective response in the visible domain. When such inclusions are embedded in a host medium, they may provide metamaterials with negative effective permeability at optical frequencies. We also show how the same inclusions may provide resonant electric dipole response and, when combining the two effects at the same frequencies, left-handed materials with both negative effective permittivity and permeability may be synthesized in the optical domain with potential applications for imaging and nano-optics applications.

Negative Refractive Index Materials

Abstract: The main directions of studies of materials with negative index of refraction, also called left-handed or metamaterials, are reviewed. First, the physics of the phenomenon of negative refraction and the history of this scientific branch are outlined. Then recent results of studies of photonic crystals that exhibit negative refraction are discussed. In the third part numerical methods for the simulation of negative index material configurations and of metamaterials that exhibit negative index properties are presented. The advantages and the shortages of existing computer packages are analyzed. Finally, details of the fabrication of different kinds of metamaterials are given. This includes composite metamaterials, photonic crystals, and transmission line metamaterials for different wavelengths namely radio frequencies, microwaves, terahertz, infrared, and visible light. Furthermore, some examples of practical applications of metamaterials are presented.

Tunable split-ring resonators for nonlinear negative-index metamaterials.

Abstract: We study experimentally the dynamic tunability and self-induced nonlinearity of split-ring resonators incorporating variable capacitance diodes. We demonstrate that the eigenfrequencies of the resonators can be tuned over a wide frequency range, and significantly, we show that the self-induced nonlinear effects observed in the varactor-loaded split-ring resonator structures can appear at relatively low power levels.

Single-slit split-ring resonators at optical frequencies: limits of size scaling.

Abstract: We present magnetic metamaterials composed of 35 nm minimum feature-size gold split-ring resonators with a fundamental magnetic resonance at a wavelength of 900 nm. Corresponding calculations reveal excellent agreement with the experiments and show that the limits of size scaling have been reached.

On the electrical characteristics of complementary metamaterial resonators

Abstract: In this letter, a method to obtain the electrical characteristics of complementary split ring resonators (CSRRs) coupled to planar transmission lines is presented. CSRRs have been recently proposed by some of the authors as new constitutive elements for the synthesis of metamaterials with negative effective permittivity, and they have been applied to the fabrication of metamaterial-based circuits in planar technology. The method provides the electrical characteristics of CSRRs (including the intrinsic resonant frequency and the unloaded Q-factor), as well as the coupling capacitance between line and CSRRs, and the parameters of the host line. Parameter extraction from the proposed method is applied to two different structures corresponding to the basic cells of left handed (LH) and negative permittivity lines. The method is of actual interest for the design of microwave circuits and metamaterials based on these complementary resonant particles

Nanowire metamaterials with extreme optical anisotropy

Abstract: The authors study perspectives of nanowire metamaterials for negative-refraction waveguides, high-performance polarizers, and polarization-sensitive biosensors. They demonstrate that the behavior of these composites is strongly influenced by the concentration, distribution, and geometry of the nanowires, derive an analytical description of electromagnetism in anisotropic nanowire-based metamaterials, and explore the limitations of their approach via three-dimensional numerical simulations. Finally, they illustrate the developed approach on the examples of nanowire-based high-energy-density waveguides and nonmagnetic negative-index imaging systems with far-field resolution of one-sixth of vacuum wavelength.

Photonic Metamaterials: Magnetism at Optical Frequencies

Abstract: Photonic metamaterials are man-made materials with "lattice constants" smaller than the wavelength of light. Tailoring the properties of their functional building blocks (atoms) allows one to go beyond the possibilities of usual materials. For example, magnetic dipole moments at optical frequencies (mune1) become possible. This aspect substantially enriches the possibilities of optics and photonics and forms the basis for the so-called negative-index metamaterials. Here, we describe the underlying physics and review the recent progress in this rapidly emerging field

Compensating losses in negative-index metamaterials by optical parametric amplification.

Abstract: Optical parametric amplification controlled by the auxiliary electromagnetic field enables transparency, amplification, and oscillation with no cavity in strongly absorbing negative-index metamaterials The opposite directions of the wave vector and the Poynting vector in such materials result in extraordinary optical properties, including "backward" phase matching and the generation of entangled pairs of left- and right-handed counterpropagating photons

Theory of linear chains of metamaterial/plasmonic particles as subdiffraction optical nanotransmission lines

Abstract: Here we discuss the theory and analyze in detail the guidance properties of linear arrays of metamaterial/plasmonic small particles as nano-scale optical nanotransmission lines, including the effect of material loss. Under the assumption of dipolar approximation for each particle, which is shown to be accurate in the geometry of interest here, we develop closed-form analytical expressions for the eigen-modal dispersion in such arrays. With the material loss included, the conditions for minimal absorption and maximum bandwidth are derived analytically by studying the properties of such dispersion relations. Numerical examples with realistic materials including their ohmic absorption and frequency dispersion are presented. The analytical properties discussed here also provide some further physical insights into the mechanisms underlying the sub-diffraction guidance in such arrays and their fundamental physical limits. Possibility of guiding beams with sub-wavelength lateral confinement and reasonably low decay is discussed offering the possible use of this technique at microwave, infrared and optical frequencies. Interpretation of these results in terms of nanocircuit concepts is presented, and possible extension to 2-D and 3-D nanotrasnsmission line optical metamaterials is also foreseen.

Spatial dispersion and negative refraction of light

Abstract: Negative refraction occurs at interfaces as a natural consequence of the negative group velocity of waves in one of the interfacing media. The historical origin of this understanding of the phenomenon is briefly discussed. We consider several physical systems that may exhibit normal electromagnetic waves (polaritons) with negative group velocity at optical frequencies. These systems are analyzed in a unified way provided by the spatial dispersion framework. The framework utilizes the notion of the generalized dielectric tensor eij(ω, k) representing the electromagnetic response of the medium to perturbations of frequency ω and wave vector k. Polaritons with negative group velocity can exist in media (whether in natural or in artificial meta-materials) with a sufficiently strong spatial dispersion. Our examples include both gyrotropic and nongyrotropic systems, and bulk and surface polariton waves. We also discuss the relation between the spatial dispersion approach and the more familiar, but more restricted, description involving the dielectric permittivity e(ω) and the magnetic permeability μ(ω) .

Negative-index materials : New frontiers in optics

Abstract: A lot of recent interest has been focused on a new class of materials, the so-called left-handed materials (LHMs) or negative-index materials, which exhibit highly unusual electromagnetic properties and hold promise for new device applications. These materials do not exist in nature and can only be fabricated artificially; for this reason, they are called metamaterials. Their unique properties are not determined by the fundamental physical properties of their constituents, but rather by the shape and distribution of the specific patterns included in them. Metamaterials can be designed to exhibit both electric and magnetic resonances that can be separately tuned to occur in frequency bands from megahertz to terahertz frequencies, and hopefully to the visible region of the electromagnetic spectrum. This article presents a short history of the field, describes the underlying physics, and reviews the experimental and theoretical status of the field at present. Many interesting questions on how to fabricate more isotropic LHMs, on how to push the operational frequency to optical wavelengths, how to reduce the losses, and how to incorporate active or nonlinear materials in LHMs remain to be explored further.

Optical nanotransmission lines: synthesis of planar left-handed metamaterials in the infrared and visible regimes

Abstract: Following our recent theoretical development of the concepts of nanoinductors, nanocapacitors, and nanoresistors at optical frequencies and the possibility of synthesizing more complex nanoscale circuits, we theoretically investigate in detail the problem of optical nanotransmission lines (NTLs) that can be envisioned by properly joining together arrays of these basic nanoscale circuit elements. We show how, in the limit in which these basic circuit elements are closely packed together, NTLs can be regarded as stacks of plasmonic and nonplasmonic planar slabs, which may be designed to effectively exhibit the properties of planar metamaterials with forward (right-handed) or backward (left-handed) operation. With the proper design, negative refraction and left-handed propagation are shown to be possible in these planar plasmonic guided-wave structures, providing possibilities for subwavelength focusing and imaging in planar optics and laterally confined waveguiding at IR and visible frequencies. The effective material parameters for such NTLs are derived, and the connection and analogy between these optical NTLs and the double-negative and double-positive metamaterials are also explored. Physical insights and justification for the results are also presented.