Showing papers on "Transformation optics published in 2006"
TL;DR: This work shows how electromagnetic fields can be redirected at will and proposes a design strategy that has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.
Abstract: 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.
7,811 citations
TL;DR: This work describes here the first practical realization of a cloak of invisibility, constructed with the use of artificially structured metamaterials, designed for operation over a band of 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.
6,830 citations
TL;DR: A general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics is developed, which can be applied to escape detection by other electromagnetic waves or sound.
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.
3,850 citations
TL;DR: In this article, a lithographically patterned inductive-capacitive resonator is described that has a strong electric response and can be used to construct metamaterials with desired positive or negative permittivity.
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.
756 citations
TL;DR: In this paper, the authors 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.
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.
581 citations
TL;DR: The main directions of studies of materials with negative index of refraction, also called left-handed or metamaterials, are reviewed in this article, where the advantages and the shortages of existing computer packages are analyzed.
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.
272 citations
TL;DR: The negative index metamaterial (NIM) as mentioned in this paper is a class of materials with lattice constants smaller than the wavelength of light that can be tailored to the properties of their functional building blocks (atoms).
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
233 citations
TL;DR: A waveguide-based retrieval method for measuring complex permittivity and permeability tensors of metamaterials is presented and shows its effectiveness in the effective parameters extraction.
Abstract: A waveguide-based retrieval method for measuring complex permittivity and permeability tensors of metamaterials is presented. In the proposed scheme, multiple independent sets of scattering data for the material under test with different orientations are measured in the frequency range corresponding to the dominant TE(10) mode. The method is applied to various metamaterials and shows its effectiveness in the effective parameters extraction.
149 citations
TL;DR: From the measured mappings of the electric field, the interplay between the microstructure of the metamaterial lattice and the macroscopic averaged response is revealed and the mapped phase fronts within a meetingamaterial having a negative refractive index are consistent with a Macroscopic phase-in accordance with the effective medium predictions.
Abstract: We perform an experimental study of the phase and amplitude of microwaves interacting with and scattered by two-dimensional negative index metamaterials. The measurements are performed in a parallel plate waveguide apparatus at X-band frequencies (8–12 GHz), thus constraining the electromagnetic fields to two dimensions. A detection antenna is fixed to one of the plates, while a second plate with a fixed source antenna or waveguide is translated relative to the first plate. The detection antenna is inserted into, but not protruding below, the stationary plate so that fields internal to the metamaterial samples can be mapped. From the measured mappings of the electric field, the interplay between the microstructure of the metamaterial lattice and the macroscopic averaged response is revealed. For example, the mapped phase fronts within a metamaterial having a negative refractive index are consistent with a macroscopic phase—in accordance with the effective medium predictions—which travels in a direction opposite to the direction of propagation. The field maps are in excellent agreement with finite element numerical simulations performed assuming homogeneous metamaterial structures.
116 citations
TL;DR: In this article, the authors review both the theoretical electromagnetic response and the spectroscopic measurements of metamaterials and discuss the complexity of extracting the optical constants from experimental observables.
Abstract: We review both the theoretical electromagnetic response and the spectroscopic measurements of metamaterials. To critically examine published results for metamaterial structures operating in the range from terahertz to optical frequencies, we focus on protocols allowing one to extract the optical constants from experimental observables. We discuss the complexity of this task when applied to metamaterials exhibiting electric, magnetic, and magneto-optical response. The general theory of the electromagnetic response of such systems is presented and methods are described. Finally, we briefly overview possible solutions for implementing metamaterials with tunable resonant behavior. © 2006 Optical Society of America OCIS codes: 160.3820, 300.6270, 120.2130, 160.4760.
57 citations
TL;DR: The general full-wave analysis shows that the obtained quasistatic conditions are useful in designing the electromagnetically transparent materials.
Abstract: With the help of the "neutral inclusion" concept, the conditions of electromagnetic wave transparency for multilayered spheres, coated spheroids, and general particulate composites are analytically derived in the quasistatic case. The basic idea is to make the effective material property of a composite region equal to that of the surrounding medium. The general full-wave analysis shows that the obtained quasistatic conditions are useful in designing the electromagnetically transparent materials.
TL;DR: In this article, double-resonant (binary) metamaterials composed of two types of magnetic resonant elements are proposed for phase-matched parametric interaction and enhanced second-harmonic generation.
Abstract: We suggest double-resonant (binary) metamaterials composed of two types of magnetic resonant elements, and demonstrate that in the nonlinear regime such metamaterials provide unique possibilities for phase-matched parametric interaction and enhanced second-harmonic generation.
TL;DR: In this article, a waveguide simulation of a unit cell is used to retrieve the effective permittivity and permeability with which they compute the far-field radiation of a monopole embedded in a metamaterial substrate using an analytic method.
Abstract: Simulations have been carried out on metamaterials in the microwave regime. S-parameters obtained from waveguide simulations of a unit cell are used to retrieve the effective permittivity and permeability with which we compute the far-field radiation of a monopole embedded in a metamaterial substrate using an analytic method. We find that the analytic method is able to predict features of the experimental results, implying that within a certain frequency range, we can treat the metamaterial as being anisotropically homogeneous. Based on the methodology, a structure is optimized for the application of metamaterials as antenna substrate to enhance directivity by minimizing its refractive index. The experimental results are presented and compared with the analytic calculations. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 680–683, 2006; Pubished online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21441
TL;DR: In this paper, the authors demonstrate the change of the polarization of the electromagnetic wave induced by chiral metamaterials in the terahertz region and demonstrate that the metal screw hole arrays work as a strong optically active material.
Abstract: The authors demonstrate the change of the polarization of the electromagnetic wave induced by chiral metamaterials in the terahertz region. The polarization of the incident terahertz wave changes dramatically after transmitting through the chiral metamaterials made of the array of screw holes in metal slabs. A strong resonant polarization change (ellipticity and polarization azimuth) is observed at frequencies corresponding to the standing cavity modes of the metal waveguide with a finite length. Such experimental results indicate that the metal screw hole arrays work as a strong optically active material.
TL;DR: In this paper, a metamaterial characterized by a constitutive relation with negative constitutive parameters is produced in solid-state form by randomizing contour patterns deposited lithographically on circuit board materials.
Abstract: Artificial metamaterials made to date are all periodic in structure. Here we show that by randomizing contour patterns deposited lithographically on circuit board materials, a metamaterial characterized by a constitutive relation with negative constitutive parameters is produced in solid-state form. We clearly demonstrate the phenomenon of negative refraction to show that it is not produced by periodicity. This underlines the importance of using constitutive relations for media characterization in electromagnetic theory and suggests that metamaterials could be realized with composite materials or fabricated with various techniques by using versatile hosting materials.
TL;DR: In this article, the polarizability properties of spherically layered small inclusions that possess negative permittivity were analyzed and conditions for invisibility to external electric fields were derived.
Abstract: This study analyzes polarizability properties of spherically layered small inclusions that possess negative permittivity. Conditions for invisibility to external electric fields are derived. The complementary principle for two-dimensional scatterers is used to derive special properties of self-complementary inclusions. A singular behavior between the limits of invisibility and infinite response is underlined for a hollow circular shell. A similar,although not as drastic,phenomenon is shown to take place for the three-dimensional hollow sphere.
01 Apr 2006
TL;DR: In this article, the 2D and 3D micro-and nanofabrication of ElectroMagnetic MetaMaterials (EM3) for the terahertz range is addressed.
Abstract: This paper addresses the 2D and 3D micro- and nanofabrication of ElectroMagnetic MetaMaterials (EM3) for the terahertz range. EM3 refers to artifbial composite materials which consist of a collection of repeated metal elements designed to have a strong response to applied electromagnetic felds, so that near resonance both the effective permittivity and magnetic permeability µ become simultaneously negative. This unusual situation leads to exotic consequences such as a negative index of refraction and an inverse Doppler and Cerenkov effect. EM3 fabricated so far have been mostly two-dimensional and in this respect are highly anisotropic. By anisotropic, it is inferred that the response of the system depends on the direction of illumination. The anisotropic nature of the metamaterials impedes eventual real-life applications of the negative media as it places constraints on the impinging electromagnetic waves. Ways of producing three-dimensional (3D) or more isotropic EM3 by means of tilted x-ray exposures will be introduced. Basic geometry tells us that if the structures are inclined at 30-45°, this would lead to an improvement of the coupling of the vector by 50-70%
TL;DR: In this paper, the authors summarize some recent activities in the field of metamaterial research at the National University of Singapore (NUS) and summarize some special characteristics of the metammaterials.
Abstract: In this paper, we summarize some recent activities in the field of metamaterial research at the National University of Singapore (NUS). Integral equations are applied for electromagnetic modelling of supernatural materials. Some special characteristics of the metamaterials are shown. Moreover, quasi-static Lorentz theory and numerical method (i.e., the method of moments for solving the electric field integral equation) and the transmission line theory are both presented to obtain the effective constitutive relations of metamaterials, respectively. Finally, feasibility of fabricating metamaterials based on analysis of equivalent transmission line model in the microwave spectrum and even higher is also shown and correspondingly some broad-bandwidth and low-loss metamaterial structures are designed and synthesized.
TL;DR: In this paper, a rigorous modeling and analysis of electromagnetic wave transformation and radiation from the periodic boundary of metamaterials is presented, where the nature of the phenomenon of resonant radiation and the influence of various parameters on it are investigated.
Abstract: The rigorous modeling and analysis of electromagnetic wave transformation and radiation from the periodic boundary of metamaterial are presented. The nature of the phenomenon of resonant radiation and the influence of various parameters on it are investigated. The study is carried out with the objective of potential applications to antenna design. Simulated results show that very high directivity can be obtained and that beam steering can be achieved by adjusting proper parameters.
05 Jun 2006
TL;DR: In this paper, the authors present new designs for metamaterials that exhibit a tailored resonant electrical response, investigated with THz time domain spectroscopy, which will significantly ease the burden of construction for future negative index metammaterial devices.
Abstract: We present new designs for metamaterials that exhibit a tailored resonant electrical response, investigated with THz time domain spectroscopy. These electric metamaterials will significantly ease the burden of construction for future negative index metamaterial devices.
TL;DR: In this paper, the ponderomotive interaction between a high-frequency modulated amplitude electric field and low-frequency potential distributions leads to spontaneous generation of magnetic fields, whose form and properties are discussed.
Abstract: We propose a possible mechanism for the generation of magnetic fields in negative refraction index composite metamaterials. Considering the propagation of a high-frequency modulated amplitude electric field in a left-handed material (LHM), we show that the ponderomotive interaction between the field and low-frequency potential distributions leads to spontaneous generation of magnetic fields, whose form and properties are discussed.
05 Jun 2006
TL;DR: In this article, a methodology to evaluate the effective parameters of a three-dimensional lattice of chiral inclusions is presented, where the homogenization is based upon mathematical arguments.
Abstract: A novel methodology to evaluate the effective parameters of a three-dimensional lattice of chiral inclusions is presented. The homogenization is based upon mathematical arguments. The finite element technique is used to compute the constitutive parameters.
06 Mar 2006
TL;DR: In this paper, a planar anisotropic metamaterial was used to achieve frequency diplexing by exploiting the inherent spatial filtering property of the hyperbolic metammaterial.
Abstract: The objective of this work is to investigate the possible use of metamaterials to achieve frequency diplexing. The metamaterial of interest is a planar anisotropic metamaterial proposed by Balmain et al. in [1]. It was shown in [2] that this metamaterial is magnetically anisotropic and could be described by a diagonal permeability tensor. For a certain range of frequencies, two of the three diagonal elements of the permeability tensor become opposite in sign. Under this condition, plane-wave propagation is governed by a hyperbolic dispersion equation and the metamaterial could be referred to as a hyperbolic metamaterial [3]. As a result, under point-source excitation, resonance cones form as a consequence of the singularity associated with the characteristic surface of the hyperbolic dispersion equation. Since the resonance cone angle, which describes the direction of power flow [4], varies with the frequency of the propagating wave, the phenomenon may properly be termed “spatial filtering.” The diplexer presented in this work exploits this inherent spatial filtering property of the hyperbolic metamaterial to achieve frequency diplexing.
01 Sep 2006
TL;DR: In this article, the authors examined several methods to determine the effective permittivity and permeability of both normal materials and metamaterials in free space and rectangular waveguide environments.
Abstract: : In the frequency domain all materials can be described electrically by their complex permittivity (micro) and permeability (micro). These constitutive parameters determine the response of the material to electromagnetic (EM) radiation. The precise knowledge of complex permittivity and permeability is required not only for scientific but also for industrial applications. Due to the uncertainties in manufacturing processes, often the only way to find a material's parameters is to measure them. The concept of metamaterials, exhibiting negative permittivity and permeability, is attracting a lot of attention. Such materials are also termed left-handed materials (LHMs). This thesis examines several methods to determine the effective permittivity and permeability of both normal materials and metamaterials. CST Microwave Studio is used to model the materials in both free space and rectangular waveguide environments to calculate the S-parameters (S11 and S21) from which the constitutive parameters can be extracted.
08 Dec 2006
TL;DR: In this article, the dispersion relation of a left-handed metamaterial-loaded waveguide has several interesting frequency bands which are described, and they have potential applications in active and passive devices at millimeter waves and at much higher frequencies.
Abstract: Metamaterials are artificial periodic structures made of small elements and designed to obtain specific electromagnetic properties. As long as the periodicity and the size of the elements are much smaller than the wavelength of interest, an artificial structure can be described by a permittivity and permeability, just like natural materials. When the permittivity and permeability are simultaneously negative in some frequency range, the metamaterial is called double negative or left‐handed and has some unusual properties. Left‐handed metamaterials (LHM) have potential applications in active and passive devices at millimeter waves and at much higher frequencies. Waveguides loaded with metamaterials are of interest because the metamaterials can change the dispersion relation of the waveguide significantly. Slow backward waves can be produced in a LHM‐loaded waveguide without corrugations. The dispersion relation of a LHM‐loaded waveguide has several interesting frequency bands which are described. Left‐hande...
01 Oct 2006
TL;DR: In this paper, the authors show that matched impedance and compensated losses due to optimized design and gain material can lead to 100% transmission in Poynting and contra-directed wave vectors.
Abstract: Calculations show that matched impedance and compensated losses due to optimized design and gain material, respectively, can lead to 100% transmission. Extraordinary nonlinear-optical properties originating from contra-directed wave and Poynting vectors are discussed.
11 Sep 2006
TL;DR: In this paper, the authors present a review of metamaterial medium modeling with effective material parameters, including permittivity and permeability, and various possible approaches to effective medium modelling.
Abstract: Various metamaterials, very actively studied in recent years, usually consist of metal inclusions of complex shapes periodically arranged in space. If the period of the lattice and the dimensions of the inclusions are small compared with the wavelength, the material is usually considered as an effectively homogeneous medium characterized by effective material parameters (permittivity and permeability). The shape and dimensions of inclusions define the electromagnetic response, which may be rather exotic (negative material parameters, for example) and resonant response. Modelling of typical metamaterial samples with effective material parameters is a non-trivial task, where one has to face several complications as compared with the "usual" materials. These complications as well as various possible approaches to effective medium modelling will be discussed in this review presentation.
TL;DR: The state of the art of electrodynamics of new composite media (metamaterials) is reviewed in this paper, where composites in the form of a periodic lattice of identical elements, which are in essence artificial crystals with characteristic scales of the internal structure from several centimeters to several hundred nanometers are considered.
Abstract: The state of the art of electrodynamics of new composite media—metamaterials—is reviewed. The composites in the form of a periodic lattice of identical elements, which are in essence artificial crystals with characteristic scales of the internal structure from several centimeters to several hundred nanometers are considered. The most important properties of metamaterials and the specific features of propagation of electromagnetic signals in these media are described. Particular attention is paid to the conventional methods of condensed-matter physics, which have found application in the electrodynamics of metamaterials and have provided dynamic development of this new field of science and technology.