Using the freedom of design that metamaterials provide, we show how electromagnetic fields can be redirected at will and propose a design strategy. The conserved fields-electric displacement field D, magnetic induction field B, and Poynting vector B-are all displaced in a consistent manner. A simple illustration is given of the cloaking of a proscribed volume of space to exclude completely all electromagnetic fields. Our work has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.

/pdf/controlling-electromagnetic-fields-3ryxkryf1t.pdf

Controlling Electromagnetic Fields

Recently, artificially constructed metamaterials have become of considerable interest, because these materials can exhibit electromagnetic characteristics unlike those of any conventional materials. Artificial magnetism and negative refractive index are two specific types of behavior that have been demonstrated over the past few years, illustrating the new physics and new applications possible when we expand our view as to what constitutes a material. In this review, we describe recent advances in metamaterials research and discuss the potential that these materials may hold for realizing new and seemingly exotic electromagnetic phenomena.

/pdf/metamaterials-and-negative-refractive-index-5ehczes1hu.pdf

Metamaterials and negative refractive index.

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.

https://science.sciencemag.org/content/sci/early/2006/05/25/science.1126493.full.pdf

Optical Conformal Mapping

Recent theory has predicted a superlens that is capable of producing sub–diffraction-limited images. This superlens would allow the recovery of evanescent waves in an image via the excitation of surface plasmons. Using silver as a natural optical superlens, we demonstrated sub–diffraction-limited imaging with 60-nanometer half-pitch resolution, or one-sixth of the illumination wavelength. By proper design of the working wavelength and the thickness of silver that allows access to a broad spectrum of subwavelength features, we also showed that arbitrary nanostructures can be imaged with good fidelity. The optical superlens promises exciting avenues to nanoscale optical imaging and ultrasmall optoelectronic devices.

http://science.sciencemag.org/content/sci/308/5721/534.full.pdf

Sub-Diffraction-Limited Optical Imaging with a Silver Superlens

Metals such as silver support surface plasmons: electromagnetic surface excitations localized near the surface that originate from the free electrons of the metal. Surface modes are also observed on highly conducting surfaces perforated by holes. We establish a close connection between the two, showing that electromagnetic waves in both materials are governed by an effective permittivity of the same plasma form. The size and spacing of holes can readily be controlled on all relevant length scales, which allows the creation of designer surface plasmons with almost arbitrary dispersion in frequency and in space, opening new vistas in surface plasmon optics.

https://science.sciencemag.org/content/sci/305/5685/847.full.pdf

Mimicking Surface Plasmons with Structured Surfaces

Recent demonstrations of negative refraction utilize three-dimensional collections of discrete periodic scatterers to synthesize artificial dielectrics with simultaneously negative permittivity and permeability. In this paper, we propose an alternate perspective on the design and function of such materials that exploits the well-known L-C distributed network representation of homogeneous dielectrics. In the conventional low-pass topology, the quantities L and C represent a positive equivalent permeability and permittivity, respectively. However, in the dual configuration, in which the positions of L and C are simply interchanged, these equivalent material parameters assume simultaneously negative values. Two-dimensional periodic versions of these dual networks are used to demonstrate negative refraction and focusing; phenomena that are manifestations of the fact that such media support a propagating fundamental backward harmonic. We hereby present the characteristics of these artificial transmission-line media and propose a suitable means of implementing them in planar form. We then present circuit and full-wave field simulations illustrating negative refraction and focusing, and the first experimental verification of focusing using such an implementation.

/pdf/planar-negative-refractive-index-media-using-periodically-l-duso1pnphm.pdf

Planar negative refractive index media using periodically L-C loaded transmission lines

Contributors. Preface. 1. Negative-Refractive-Index Transmission-Line Metamaterials (A. Iyer & G. Eleftheriades). 2. Passive Microwave Devices and Antennas Using Negative-Refractive-Index Transmission-Line Metamaterials (G. Eleftheriades). 3. Super Resolving Negative-Refractive-Index Transmission-Line Lenses (A. Grbic & G. Eleftheriades). 4. Gaussian Beam Interactions with DNG Metamaterials (R. Ziolkowski). 5. Negative Index Lenses (D. Schurig & D. Smith). 6. Planar Anisotropic Resonance-Cone Metamaterials (K. balmain & A. Luttgen). 7. Negative Refraction and Subwavelength Imaging in Photonic Crystals (C. Luo & J. Joannopoulos). 8. Plasmonic Nanowire Metamaterials (A. Sarychev & V. Shalaev). 9. An Overview of Salient Properties of Planar Guided-Wave Structures with Double-Negative (DNG) and Single-Negative (SNG) Layers (A Alu and N. Engheta). 10. Dispersion Engineering: The Use of Abnormal Velocities and Negative Index of Refraction to Control the Dispersive Effects (M. Mojahedi & G. Eleftheriades). Index.

Negative-Refraction Metamaterials: Fundamental Principles and Applications

We report experimental results at 1.057 GHz that demonstrate the ability of a planar left-handed lens, with a relative refractive index of $\ensuremath{-}1$, to form images that overcome the diffraction limit. The left-handed lens is a planar slab consisting of a grid of printed metallic strips over a ground plane, loaded with series capacitors ($C$) and shunt inductors ($L$). The measured half-power beamwidth of the point-source image formed by the left-handed lens is 0.21 effective wavelengths, which is significantly narrower than that of the diffraction-limited image corresponding to 0.36 wavelengths.

https://waves.utoronto.ca/prof/gelefth/Backup_Old/gelefth/jpub/PRL17403.pdf

Overcoming the diffraction limit with a planar left-handed transmission-line lens.

Overcoming the Diffraction Limit with a Planar Left-Handed Transmission-Line Lens

A composite medium consisting of an array of fine wires and split-ring resonators has been previously used to experimentally verify a negative index of refraction. We present a negative refractive index (NRI) metamaterial that goes beyond the original split-ring resonator/wire medium and is capable of supporting a backward cone of radiation. We report experimental results at microwave frequencies that demonstrate backward-wave radiation from a NRI metamaterial—a characteristic analogous to reversed Cherenkov radiation. The conception of this metamaterial is based on a fresh perspective regarding the operation of NRI metamaterials.

George V. Eleftheriades

Papers

Planar negative refractive index media using periodically L-C loaded transmission lines

Negative-Refraction Metamaterials: Fundamental Principles and Applications

Overcoming the diffraction limit with a planar left-handed transmission-line lens.

Overcoming the Diffraction Limit with a Planar Left-Handed Transmission-Line Lens

Experimental verification of backward-wave radiation from a negative refractive index metamaterial