Showing papers on "Metamaterial published in 2005"
11 Nov 2005
TL;DR: In this paper, the authors define Metamaterials (MTMs) and Left-Handed (LH) MTMs as a class of two-dimensional MTMs.
Abstract: Preface. Acknowledgments. Acronyms. 1 Introduction. 1.1 Definition of Metamaterials (MTMs) and Left-Handed (LH) MTMs. 1.2 Theoretical Speculation by Viktor Veselago. 1.3 Experimental Demonstration of Left-Handedness. 1.4 Further Numerical and Experimental Confirmations. 1.5 "Conventional" Backward Waves and Novelty of LH MTMs. 1.6 Terminology. 1.7 Transmission Line (TL) Approach. 1.8 Composite Right/Left-Handed (CRLH) MTMs. 1.9 MTMs and Photonic Band-Gap (PBG) Structures. 1.10 Historical "Germs" of MTMs. References. 2 Fundamentals of LH MTMs. 2.1 Left-Handedness from Maxwell's Equations. 2.2 Entropy Conditions in Dispersive Media. 2.3 Boundary Conditions. 2.4 Reversal of Doppler Effect. 2.5 Reversal of Vavilov- Cerenkov Radiation. 2.6 Reversal of Snell's Law: Negative Refraction. 2.7 Focusing by a "Flat LH Lens". 2.8 Fresnel Coefficients. 2.9 Reversal of Goos-H anchen Effect. 2.10 Reversal of Convergence and Divergence in Convex and Concave Lenses. 2.11 Subwavelength Diffraction. References. 3 TLTheoryofMTMs. 3.1 Ideal Homogeneous CRLH TLs. 3.1.1 Fundamental TL Characteristics. 3.1.2 Equivalent MTM Constitutive Parameters. 3.1.3 Balanced and Unbalanced Resonances. 3.1.4 Lossy Case. 3.2 LC Network Implementation. 3.2.1 Principle. 3.2.2 Difference with Conventional Filters. 3.2.3 Transmission Matrix Analysis. 3.2.4 Input Impedance. 3.2.5 Cutoff Frequencies. 3.2.6 Analytical Dispersion Relation. 3.2.7 Bloch Impedance. 3.2.8 Effect of Finite Size in the Presence of Imperfect Matching. 3.3 Real Distributed 1D CRLH Structures. 3.3.1 General Design Guidelines. 3.3.2 Microstrip Implementation. 3.3.3 Parameters Extraction. 3.4 Experimental Transmission Characteristics. 3.5 Conversion from Transmission Line to Constitutive Parameters. References. 4 Two-Dimensional MTMs. 4.1 Eigenvalue Problem. 4.1.1 General Matrix System. 4.1.2 CRLH Particularization. 4.1.3 Lattice Choice, Symmetry Points, Brillouin Zone, and 2D Dispersion Representations. 4.2 Driven Problem by the Transmission Matrix Method (TMM). 4.2.1 Principle of the TMM. 4.2.2 Scattering Parameters. 4.2.3 Voltage and Current Distributions. 4.2.4 Interest and Limitations of the TMM. 4.3 Transmission Line Matrix (TLM) Modeling Method. 4.3.1 TLM Modeling of the Unloaded TL Host Network. 4.3.2 TLM Modeling of the Loaded TL Host Network (CRLH). 4.3.3 Relationship between Material Properties and the TLM Model Parameters. 4.3.4 Suitability of the TLM Approach for MTMs. 4.4 Negative Refractive Index (NRI) Effects. 4.4.1 Negative Phase Velocity. 4.4.2 Negative Refraction. 4.4.3 Negative Focusing. 4.4.4 RH-LH Interface Surface Plasmons. 4.4.5 Reflectors with Unusual Properties. 4.5 Distributed 2D Structures. 4.5.1 Description of Possible Structures. 4.5.2 Dispersion and Propagation Characteristics. 4.5.3 Parameter Extraction. 4.5.4 Distributed Implementation of the NRI Slab. References. 5 Guided-Wave Applications. 5.1 Dual-Band Components. 5.1.1 Dual-Band Property of CRLH TLs. 5.1.2 Quarter-Wavelength TL and Stubs. 5.1.3 Passive Component Examples: Quadrature Hybrid and Wilkinson Power Divider. 5.1.3.1 Quadrature Hybrid. 5.1.3.2 Wilkinson Power Divider. 5.1.4 Nonlinear Component Example: Quadrature Subharmonically Pumped Mixer. 5.2 Enhanced-Bandwidth Components. 5.2.1 Principle of Bandwidth Enhancement. 5.2.2 Rat-Race Coupler Example. 5.3 Super-compact Multilayer "Vertical" TL. 5.3.1 "Vertical" TL Architecture. 5.3.2 TL Performances. 5.3.3 Diplexer Example. 5.4 Tight Edge-Coupled Coupled-Line Couplers (CLCs). 5.4.1 Generalities on Coupled-Line Couplers. 5.4.1.1 TEM and Quasi-TEM Symmetric Coupled-Line Structures with Small Interspacing: Impedance Coupling (IC). 5.4.1.2 Non-TEM Symmetric Coupled-Line Structures with Relatively Large Spacing: Phase Coupling (PC). 5.4.1.3 Summary on Symmetric Coupled-Line Structures. 5.4.1.4 Asymmetric Coupled-Line Structures. 5.4.1.5 Advantages of MTM Couplers. 5.4.2 Symmetric Impedance Coupler. 5.4.3 Asymmetric Phase Coupler. 5.5 Negative and Zeroth-Order Resonator. 5.5.1 Principle. 5.5.2 LC Network Implementation. 5.5.3 Zeroth-Order Resonator Characteristics. 5.5.4 Circuit Theory Verification. 5.5.5 Microstrip Realization. References. 6 Radiated-Wave Applications. 6.1 Fundamental Aspects of Leaky-Wave Structures. 6.1.1 Principle of Leakage Radiation. 6.1.2 Uniform and Periodic Leaky-Wave Structures. 6.1.2.1 Uniform LW Structures. 6.1.2.2 Periodic LW Structures. 6.1.3 Metamaterial Leaky-Wave Structures. 6.2 Backfire-to-Endfire (BE) Leaky-Wave (LW) Antenna. 6.3 Electronically Scanned BE LW Antenna. 6.3.1 Electronic Scanning Principle. 6.3.2 Electronic Beamwidth Control Principle. 6.3.3 Analysis of the Structure and Results. 6.4 Reflecto-Directive Systems. 6.4.1 Passive Retro-Directive Reflector. 6.4.2 Arbitrary-Angle Frequency Tuned Reflector. 6.4.3 Arbitrary-Angle Electronically Tuned Reflector. 6.5 Two-Dimensional Structures. 6.5.1 Two-Dimensional LW Radiation. 6.5.2 Conical-Beam Antenna. 6.5.3 Full-Space Scanning Antenna. 6.6 Zeroth Order Resonating Antenna. 6.7 Dual-Band CRLH-TL Resonating Ring Antenna. 6.8 Focusing Radiative "Meta-Interfaces". 6.8.1 Heterodyne Phased Array. 6.8.2 Nonuniform Leaky-Wave Radiator. References. 7 The Future of MTMs. 7.1 "Real-Artificial" Materials: the Challenge of Homogenization. 7.2 Quasi-Optical NRI Lenses and Devices. 7.3 Three-Dimensional Isotropic LH MTMs. 7.4 Optical MTMs. 7.5 "Magnetless" Magnetic MTMs. 7.6 Terahertz Magnetic MTMs. 7.7 Surface Plasmonic MTMs. 7.8 Antenna Radomes and Frequency Selective Surfaces. 7.9 Nonlinear MTMs. 7.10 Active MTMs. 7.11 Other Topics of Interest. References. Index.
2,750 citations
TL;DR: It is shown here that a modification of the standard S-parameter retrieval procedure yields physically reasonable values for the retrieved electromagnetic parameters, even when there is significant inhomogeneity within the unit cell of the structure.
Abstract: We discuss the validity of standard retrieval methods that assign bulk electromagnetic properties, such as the electric permittivity « and the magnetic permeability m, from calculations of the scattering sSd parameters for finite-thickness samples. S-parameter retrieval methods have recently become the principal means of characterizing artificially structured metamaterials, which, by nature, are inherently inhomogeneous. While the unit cell of a metamaterial can be made considerably smaller than the free space wavelength, there remains a significant variation of the phase across the unit cell at operational frequencies in nearly all metamaterial structures reported to date. In this respect, metamaterials do not rigorously satisfy an effective medium limit and are closer conceptually to photonic crystals. Nevertheless, we show here that a modification of the standard S-parameter retrieval procedure yields physically reasonable values for the retrieved electromagnetic parameters, even when there is significant inhomogeneity within the unit cell of the structure. We thus distinguish a metamaterial regime, as opposed to the effective medium or photonic crystal regimes, in which a refractive index can be rigorously established but where the wave impedance can only be approximately defined. We present numerical simulations on typical metamaterial structures to illustrate the modified retrieval algorithm and the impact on the retrieved material parameters. We find that no changes to the standard retrieval procedures are necessary when the inhomogeneous unit cell is symmetric along the propagation axis; however, when the unit cell does not possess this symmetry, a modified procedure—in which a periodic structure is assumed—is required to obtain meaningful electromagnetic material parameters. DOI: 10.1103/PhysRevE.71.036617
2,565 citations
TL;DR: A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range, which results from the plasmon resonance in the pairs of nanorod for both the electric and the magnetic components of light.
Abstract: A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic components of light. The refractive index is retrieved from direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with simulations. Both experiments and simulations demonstrate that a negative refractive index n???0.3 is achieved at the optical communication wavelength of 1.5??m using the array of nanorods. The retrieved refractive index critically depends on the phase of the transmitted wave, which emphasizes the importance of phase measurements in finding n?.
1,567 citations
TL;DR: Here it is seen how a proper design of these lossless metamaterial covers near their plasma resonance may induce a dramatic drop in the scattering cross section, making these objects nearly "invisible" or "transparent" to an outside observer--a phenomenon with obvious applications for low-observability and noninvasive probe design.
Abstract: The possibility of using plasmonic and metamaterial covers to drastically reduce the total scattering cross section of spherical and cylindrical objects is discussed. While it is intuitively expected that increasing the physical size of an object may lead to an increase in its overall scattering cross section, here we see how a proper design of these lossless metamaterial covers near their plasma resonance may induce a dramatic drop in the scattering cross section, making these objects nearly "invisible" or "transparent" to an outside observer--a phenomenon with obvious applications for low-observability and noninvasive probe design. Physical insights into this phenomenon and some numerical results are provided.
1,557 citations
TL;DR: In this paper, a new approach for the development of planar metamaterial structures is developed, and analytical equivalent circuit models are proposed for isolated and coupled split-ring resonators/CSRRs coupled to planar transmission lines.
Abstract: In this paper, a new approach for the development of planar metamaterial structures is developed. For this purpose, split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs) coupled to planar transmission lines are investigated. The electromagnetic behavior of these elements, as well as their coupling to the host transmission line, are studied, and analytical equivalent-circuit models are proposed for the isolated and coupled SRRs/CSRRs. From these models, the stopband/passband characteristics of the analyzed SRR/CSRR loaded transmission lines are derived. It is shown that, in the long wavelength limit, these stopbands/passbands can be interpreted as due to the presence of negative/positive values for the effective /spl epsiv/ and /spl mu/ of the line. The proposed analysis is of interest in the design of compact microwave devices based on the metamaterial concept.
1,405 citations
TL;DR: The first fabrication and experimental verification of a transversely structured metal-dielectric-metal multilayer exhibiting a negative refractive index around 2 microm is reported.
Abstract: Metal-based negative refractive-index materials have been extensively studied in the microwave region. However, negative-index metamaterials have not been realized at near-IR or visible frequencies due to difficulties of fabrication and to the generally poor optical properties of metals at these wavelengths. In this Letter, we report the first fabrication and experimental verification of a transversely structured metal-dielectricmetal multilayer exhibiting a negative refractive index around 2 mu m. Both the amplitude and the phase of the transmission and reflection were measured experimentally, and are in good agreement with a rigorous coupled wave analysis.
1,225 citations
02 Aug 2005
TL;DR: In this article, the authors proposed a planar guided-wave structure with double-negative (DNG) and single-negative (SNG) layers, and showed the properties of the planar guide-wave structures with DNG and SNG layers.
Abstract: 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.
1,050 citations
TL;DR: In this article, the existence of surface electromagnetic modes in corrugated surfaces of perfect conductors was explored and it was shown that these structures support surface bound states and that the dispersions of these modes have strong similarities with the dispersion of surface plasmon polariton bands of real metals.
Abstract: In this paper we explore the existence of surface electromagnetic modes in corrugated surfaces of perfect conductors. We analyse two cases: one-dimensional arrays of grooves and two-dimensional arrays of holes. In both cases we find that these structures support surface bound states and that the dispersions of these modes have strong similarities with the dispersion of the surface plasmon polariton bands of real metals. Importantly, the dispersion relation of these surface states is mainly dictated by the geometry of the grooves or holes and these results open the possibility of tailoring the properties of these modes by just tuning the geometrical parameters of the surface.
924 citations
TL;DR: This work identifies a novel higher-order magnetic resonance at around 370 THz (800 nm wavelength) that evolves out of the Mie resonance for oblique incidence and shows that the structures allow for a negative magnetic permeability.
Abstract: Arrays of gold split rings with a 50-nm minimum feature size and with an LC resonance at 200 THz frequency (1.5 microm wavelength) are fabricated. For normal-incidence conditions, they exhibit a pronounced fundamental magnetic mode, arising from a coupling via the electric component of the incident light. For oblique incidence, a coupling via the magnetic component is demonstrated as well. Moreover, we identify a novel higher-order magnetic resonance at around 370 THz (800 nm wavelength) that evolves out of the Mie resonance for oblique incidence. Comparison with theory delivers good agreement and also shows that the structures allow for a negative magnetic permeability.
789 citations
TL;DR: A nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level exhibits a strong magnetic response at visible-light frequencies, including a band with negative µ.
Abstract: A great deal of attention has recently been focused on a new class of smart materials-so-called left-handed media-that exhibit highly unusual electromagnetic properties and promise new device applications. Left-handed materials require negative permeability ν, an extreme condition that has so far been achieved only for frequencies in the microwave to terahertz range. Extension of the approach described in ref. 7 to achieve the necessary high-frequency magnetic response in visible optics presents a formidable challenge, as no material-natural or artificial-is known to exhibit any magnetism at these frequencies. Here we report a nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level. The medium exhibits a strong magnetic response at visible-light frequencies, including a band with negative ν. The magnetism arises owing to the excitation of an antisymmetric plasmon resonance. The high-frequency permeability qualitatively reveals itself via optical impedance matching. Our results demonstrate the feasibility of engineering magnetism at visible frequencies and pave the way towards magnetic and left-handed components for visible optics. © 2005 Nature Publishing Group.
569 citations
TL;DR: A more pronounced optical response is obtained for arrays of plate pairs, a geometry that also eliminates the undesirable polarization anisotropy of the cut-wire pairs, revealing negative magnetic permeability in the range of telecommunications wavelengths.
Abstract: We study the optical properties of metamaterials made from cut-wire pairs or plate pairs. We obtain a more pronounced optical response for arrays of plate pairs, a geometry that also eliminates the undesirable polarization anisotropy of the cut-wire pairs. The measured optical spectra agree with simulations, revealing negative magnetic permeability in the range of telecommunications wavelengths. Thus nanoscopic plate pairs might serve as an alternative to the established split-ring resonator design.
TL;DR: In this article, the authors introduce several different design methodologies for multiband artificial magnetic conducting (AMC) surfaces, based on the introduction of FSS screens that have fractal or nearly fractal unit cell geometries.
Abstract: This paper introduces several different design methodologies for multiband artificial magnetic conducting (AMC) surfaces. The paper begins by investigating the multiband properties exhibited by a conventional electromagnetic bandgap (EBG) AMC that consists of a frequency selective surface (FSS) on top of a thin dielectric substrate with a PEC back plane. The higher-order resonances associated with these surfaces have not been discussed in detail to date, as previous research has been concerned only with exploiting the primary resonant frequency. However, it will be shown that by understanding and making appropriate use of these higher order resonances, it is possible to design multiband AMC surfaces that work for nearly any desired combination of operating frequencies. The first multiband AMC design approach that will be considered is based on the introduction of FSS screens that have fractal or nearly fractal unit cell geometries. This is followed by a more general and robust genetic algorithm (GA) technique for the synthesis of optimal multiband AMC surfaces. In this case, a GA is used to evolve multiband AMC surface designs by simultaneously optimizing the geometry and size of the FSS unit cell as well as the thickness and dielectric constant of the substrate material. Finally, several examples of multiband AMC surfaces are presented, including some practical dual-band and tri-band designs genetically evolved for operation at GPS and cellular frequencies, as well as an example illustrating the success in creating a multiband AMC surface with angular stability.
TL;DR: The gradient index metamaterial proposed may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated and may prove an advantageous alternative approach to the development of gradient index lenses and similar optics.
Abstract: Metamaterials—artificially structured materials with tailored electromagnetic response—can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators sSRRsd, which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.
26 Sep 2005
TL;DR: Interferometric lithography (IL), the interference of a small number of coherent optical beams, is a powerful technique for the fabrication of a wide array of samples of interest for nanoscience and nanotechnology.
Abstract: Interferometric lithography (IL), the interference of a small number of coherent optical beams, is a powerful technique for the fabrication of a wide array of samples of interest for nanoscience and nanotechnology. The techniques and limits of IL are discussed with particular attention to the smallest scales achievable. With immersion techniques, the smallest pattern size for a single exposure is a half-pitch of /spl lambda//4n where /spl lambda/ is the optical wavelength and n is the refractive index of the immersion material. Currently with a 193-nm excimer laser source and H/sub 2/O immersion, this limiting dimension is /spl sim/34 nm. With nonlinear spatial frequency multiplication techniques, this limit is extended by factors of 1/2, 1/3, etc.-extending well into the nanoscale regime. IL provides an inexpensive, large-area capability as a result of its parallelism. Multiple exposures, multiple beams, and mix-and-match with other lithographies extend the range of applicability. Imaging IL provides an approach to arbitrary structures with comparable resolution. Numerous application areas, including nanoscale epitaxial growth for semiconductor heterostructures; nanofluidics for biological separations; nanomagnetics for increased storage density; nanophotonics including distributed feedback and distributed Bragg reflectors, two- and three-dimensional photonic crystals, metamaterials, and negative refractive index materials for enhanced optical interactions are briefly reviewed.
TL;DR: A metamaterial with both negative epsilon and negative mu over an overlapping near-infrared wavelength range resulting in a low loss negative-index material that can be easily fabricated with standard semiconductor processing techniques.
Abstract: We numerically demonstrate a metamaterial with both negative e and negative µ over an overlapping near-infrared wavelength range resulting in a low loss negative-index material. Parametric studies optimizing this negative index are presented. This structure can be easily fabricated with standard semiconductor processing techniques.
TL;DR: In this article, the authors introduce a mechanism for creating artificial high refractive index metamaterials by exploiting the existence of subwavelength propagating modes in metallic systems, which can be made arbitrarily large.
Abstract: We introduce a mechanism for creating artificial high refractive index metamaterials by exploiting the existence of subwavelength propagating modes in metallic systems. As an example, we investigate analytically and numerically metal films with a periodic arrangement of cut-through slits. Because of the presence of TEM modes in the slits, for TM polarization such a system can be rigorously mapped into a high refractive index dielectric slab when the features are smaller than the wavelength of light. The effective refractive index is entirely controlled by the geometry of the metal films, is positive, frequency independent, and can be made arbitrarily large.
TL;DR: In this article, simulations are done on the radiation of a dipole antenna embedded in metamaterial substrates, which are composed of a periodic collection of rods, or of both rods and rings.
Abstract: Using a commercial software, simulations are done on the radiation of a dipole antenna embedded in metamaterial substrates. Metamaterials under consideration are composed of a periodic collection of rods, or of both rods and rings. The S-parameters of these metamaterials in a waveguide are analyzed and compared with their equivalent plasma or resonant structure. Farfield radiation is optimized by analytic method and is simulated numerically. The metamaterial is shown to improve the directivity.
TL;DR: In this article, a rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability was investigated both theoretically and experimentally, and it was shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus it can be considered as a dual of the ordinary waveguide.
Abstract: A rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability is investigated both theoretically and experimentally. It is shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus, it can be considered as a dual of the ordinary waveguide. The transversal dimension of this waveguide can be arbitrarily smaller than half of a wavelength in the filling material, provided that the transversal permeability is negative. This peculiar behavior may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides loaded with double ring resonators in 7 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave passband located below the cutoff frequency. Furthermore, it was experimentally shown that the increase of the physical length of the waveguide caused the decrease of the electrical length. This is a direct proof of the backward-wave propagation since the phase of the backward wave increases along the waveguide.
TL;DR: In this article, the frequency dependence of the effective electromagnetic parameters of left-handed and related metamaterials of the split ring resonator and wire type was studied and a periodic effective medium model was proposed to distinguish the resonant behavior of electromagnetic parameters from effects of the periodicity of the structure.
Abstract: We study the frequency dependence of the effective electromagnetic parameters of left-handed and related metamaterials of the split ring resonator and wire type. We show that the reduced translational symmetry speriodic structured inherent to these metamaterials influences their effective electromagnetic response. To anticipate this periodicity, we formulate a periodic effective medium model which enables us to distinguish the resonant behavior of electromagnetic parameters from effects of the periodicity of the structure. We use this model for the analysis of numerical data for the transmission and reflection of periodic arrays of split ring resonators, thin metallic wires, cut wires, as well as the left-handed structures. The present method enables us to identify the origin of the previously observed resonance-antiresonance coupling as well as the occurrence of negative imaginary parts in the effective permittivities and permeabilities of those materials. Our analysis shows that the periodicity of the structure can be neglected only for the wavelength of the electromagnetic wave larger than 30 space periods of the investigated structure.
TL;DR: In this paper, a volumetric metamaterial realization of an artificial magnetic conductor (AMC) is presented, and the performance of a dipole antenna radiating in the presence of this metammaterial AMC is quantified numerically.
Abstract: The design, fabrication and measurement of a volumetric metamaterial realization of an artificial magnetic conductor (AMC) is presented. In contrast to most current realizations of AMCs, such as the mushroom and the uniplanar compact photonic bandgap surfaces, the present design has no perfect electric conductor ground plane. The perfect magnetic conductor properties were designed with capacitively loaded loops for X band operation at 10 GHz. Very good agreement between the numerical and experimental scattering results was achieved. The performance of a dipole antenna radiating in the presence of this volumetric metamaterial AMC is quantified numerically. Resonant interactions of the antenna and metamaterial structure lead to a significant enhancement of the radiated field amplitudes and isolation measured as the front-to-back ratio.
TL;DR: The method is verified both analytically and numerically, and it is shown that the results for various split-ring resonator metamaterials qualitatively corroborate the conclusions found in published papers.
Abstract: We propose a method to retrieve the effective constitutive parameters of a slab of bianisotropic metamaterial composed of split-ring resonators from the measurement of the $S$ parameters. Analytical inversion equations are derived for homogeneous lossless bianisotropic media, and a numerical retrieval approach is presented for the case of lossy bianisotropic media. The method is verified both analytically and numerically, and it is shown that the results for various split-ring resonator metamaterials qualitatively corroborate the conclusions found in published papers. The proposed retrieval method can be used as a valuable tool for the study of anisotropic and bianisotropic properties of metamaterials.
TL;DR: It is shown that surface-bound modes in metamaterials forged by drilling periodic hole arrays in perfect-conductor surfaces cannot be described in general by local, frequency-dependent permitivities and permeabilities for small periods compared to the wavelength, except in certain limiting cases that are discussed in detail.
Abstract: Surface-bound modes in metamaterials forged by drilling periodic hole arrays in perfect-conductor surfaces are investigated by means of both analytical techniques and rigorous numerical solution of Maxwell's equations. It is shown that these metamaterials cannot be described in general by local, frequency-dependent permittivities and permeabilities for small periods compared to the wavelength, except in certain limiting cases that are discussed in detail. New related metamaterials are shown to exhibit exciting optical properties that are elucidated in the light of our simple analytical approach.
TL;DR: In this paper, a negative effective permeability is shown to exist at infrared frequencies in a three-dimensional collection of polaritonic spheres, which is demonstrated by an effective medium theory which relates the Mie resonances of the constituent spheres to the bulk response of the composite.
Abstract: A negative effective permeability is shown to exist at infrared frequencies in a three-dimensional collection of polaritonic spheres This is demonstrated by an effective medium theory which relates the Mie resonances of the constituent spheres to the bulk response of the composite The derived permittivity and permeability are shown to be isotropic The results are verified by a comparison with multiple-scattering photonic band calculations The existence of an anomalous dispersion region with a negative group velocity and the appropriate signs associated with the imaginary parts of the permittivity and permeability are also discussed
TL;DR: A new set of artificial structures which can exhibit a negative refractive index band in excess of 6% in a broad frequency range from the deep infrared to the terahertz region are presented.
Abstract: We present a new set of artificial structures which can exhibit a negative refractive index band in excess of 6% in a broad frequency range from the deep infrared to the terahertz region. The structures are composites of two different kinds of non-overlapping spheres, one made from inherently non-magnetic polaritonic and the other from a Drude-like material. The polaritonic spheres are responsible for the existence of negative effective magnetic permeability whils tt he Drude-like spheres are responsible for negative effective electric permittivity. The resulting negative refractive index structures are truly subwavelength structures with wavelength-to-structure ratio 14:1, which is almost 50% higher than has been previously achieved. Our results are explained in the context of the extended Maxwell–Garnett theory and are reproduced by calculations based on the layer Korringa–Kohn–Rostoker method, an ab initio multiple scattering theory. The role of absorption in the constituent materials is discussed. Effective medium computer F77 code is freely available at http://www.wave-scattering.com
01 Mar 2005
TL;DR: In this paper, the authors present results on a new metamaterial design that employs superconducting Niobium metals and low-loss dielectric materials to reduce the losses.
Abstract: Evanescent wave amplification has been predicted under the ideal condition n = -1 + i 0 precisely, in the absence of retardation effects, but is difficult to observe in practice because current metamaterial designs suffer from high losses We present results on a new metamaterial design that employs superconducting Niobium metals and low-loss dielectric materials to reduce the losses We present transmission data on a wire medium, a split-ring resonator medium, and a combination of the two at temperatures between 42 K and room temperature Evidence of negative effective permittivity, permeability, and a negative effective index passband are seen in the superconducting state between 50 MHz and 18 GHz We find a dielectric loss of \epsilon_{eff,2} = 3 x 10^{-3} in a superconducting wire array at 1075 GHz
TL;DR: In this paper, a double-plate resonance cavity made with metamaterials was used to demonstrate a mechanism for directive emissions, which is significantly thinner than the working wavelength and requires a smaller lateral size.
Abstract: We use experiment and theory to demonstrate a mechanism for directive emissions, which involves a double-plate resonance cavity made with metamaterials. In contrast to other mechanisms employing Fabry-Perot cavities, photonic crystals, or zero index materials, our system is significantly thinner than the working wavelength and requires a smaller lateral size. We show the physics to be governed by subwavelength resonance modes unique to such metamaterial-based cavities.
TL;DR: In this paper, negative index materials (NIM) or double negative (ONG) media or left handed (LH) materials or backward wave (BW) media have been proposed.
Abstract: Metamaterials are new artificial materials with unusual electromagnetic properties that are not found in naturally occurring materials. All "natural" materials such as glass, diamond and such have positive electrical permittivity, magnetic permeability and an index of refraction. In these new artificially fabricated materials - termed as negative index materials (NIM) or double negative (ONG) media or left handed (LH) materials or backward wave (BW) media - all these material parameters are negative. With these unusual material parameters, new kinds of miniaturized antennas and microwave components/devices can be created for the wireless communications and the defense industries. The electrical permittivity and the magnetic permeability are the main determinants of a material's response to electromagnetic (EM) waves. In metamaterials, both these material parameters are negative. Correspondingly, the refractive index of the metamaterials is also negative. Another strange property of metamaterials is its reverse Doppler effect.
TL;DR: In this paper, the design and analysis of planar circularly symmetric (PCS) electromagnetic band gap (EBG) structures for reducing the surface waves excited by printed antennas on dense dielectric substrates are discussed.
Abstract: This paper discusses the design and analysis of planar circularly symmetric (PCS) electromagnetic band gap (EBG) structures for reducing the surface waves excited by printed antennas on dense dielectric substrates. The key advantage of the circularly symmetric geometries is that a surface wave generated by a source located at its center experiences the same band gap effect in all radial directions. To obtain simple design rules of the PCS-EBGs for the optimization of the bandwidth, an equivalence is established between 2-D-EBGs and PCS-EBGs. Integrated planar printed antennas with bandwidths up to 20% are designed, manufactured and tested.
TL;DR: In this article, a three-dimensional s3Dd isotropic LHM design that allows left-handed behavior for any direction of propagation and any polarization of the electromagnetic wave was proposed.
Abstract: We investigate three-dimensional left-handed and related metamaterials based on a fully symmetric multigap single-ring split-ring resonator sSRRd design and crossing continuous wires We demonstrate isotropic transmission properties of a SRR-only metamaterial and the corresponding left-handed material that possesses a negative effective index of refraction due to simultaneously negative effective permeability and permittivity Minor deviations from complete isotropy are due to the finite thickness of the metamaterial The realization of a perfect lens 1 and other applications of negative refraction require the fabrication of threedimensional, homogeneous, isotropic left-handed materials 2 sLHMd with simultaneously negative permittivity « and magnetic permeability m So far, no such materials exist, either in nature or in the laboratory Today’s available LHM structures, based on the periodic arrangement of split-ring resonators 3 sSRRd and continuous metallic wires, 4 are only one dimensional 5‐7 s1Dd, supporting left-handed properties only for propagation with fixed polarization in one direction, or two dimensional 8‐10 s2Dd, where propagation in two directions with fixed polarization or one direction with arbitrary polarization is possible Earlier attempts to design at least an isotropic SRR sRef 11d were lacking the symmetry of SRR and unit cell and required individual tuning of the parameters in the different spatial directions In this paper, we propose a three-dimensional s3Dd isotropic LHM design that allows left-handed behavior for any direction of propagation and any polarization of the electromagnetic wave Using numerical transfer matrix simulations, we verify the isotropic transmission properties of the proposed structures Our data show excellent agreement with results expected for a homogeneous slab with the corresponding negative « and m Our metamaterials are defined as a 3D periodic continuation of a single rectangular unit cell, consisting of SRRs and continuous wires The sample is a slab of metamaterial with a finite thickness of an integral number of unit cells and infinite extent in the perpendicular direction The two surfaces of the slab are parallel to any face of the unit cell An incident electromagnetic plane wave with wave vector k can be characterized by two angles: the incidence angle q P f 0, p /2 d between k and the surface normal n of the sample, and the angle f P s˛p , pg between the projection of k into and some chosen edge of the unit cell inside the surface plane of the sample The frequency of the incident wave is chosen such that the vacuum wavelength is approximately 10 times larger than the linear size of the unit cell and we expect effective medium behavior
TL;DR: In this paper, it was shown that the LC resonance frequency scales with the lateral size of the SRR, provided that all pa-rameters are simultaneously scaled down and provided that the resonance frequency does not come close to the metalplasma frequency.
Abstract: brought about by the ends ofthe wire. In the following, such a circuit will be referred to asan LC circuit. The oscillating current in the LC circuit leads toa magnetic moment perpendicular to the plane shown in Fig-ure 1A. It is known that the LC resonance frequency scalesinversely with the lateral size of the SRR, provided that all pa-rameters are simultaneously scaled down and provided thatthe resonance frequency does not come close to the metalplasma frequency. For example, for the structures describedby Linden et al.