Showing papers on "Metamaterial published in 2001"

Experimental Verification of a Negative Index of Refraction

Abstract: We present experimental scattering data at microwave frequencies on a structured metamaterial that exhibits a frequency band where the effective index of refraction (n) is negative. The material consists of a two-dimensional array of repeated unit cells of copper strips and split ring resonators on interlocking strips of standard circuit board material. By measuring the scattering angle of the transmitted beam through a prism fabricated from this material, we determine the effective n, appropriate to Snell's law. These experiments directly confirm the predictions of Maxwell's equations that n is given by the negative square root of epsilon.mu for the frequencies where both the permittivity (epsilon) and the permeability (mu) are negative. Configurations of geometrical optical designs are now possible that could not be realized by positive index materials.

Wave propagation in media having negative permittivity and permeability

Abstract: Wave propagation in a double negative (DNG) medium, i.e., a medium having negative permittivity and negative permeability, is studied both analytically and numerically. The choices of the square root that leads to the index of refraction and the wave impedance in a DNG medium are determined by imposing analyticity in the complex frequency domain, and the corresponding wave properties associated with each choice are presented. These monochromatic concepts are then tested critically via a one-dimensional finite difference time domain (FDTD) simulation of the propagation of a causal, pulsed plane wave in a matched, lossy Drude model DNG medium. The causal responses of different spectral regimes of the medium with positive or negative refractive indices are studied by varying the carrier frequency of narrowband pulse excitations. The smooth transition of the phenomena associated with a DNG medium from its early-time nondispersive behavior to its late-time monochromatic response is explored with wideband pulse excitations. These FDTD results show conclusively that the square root choice leading to a negative index of refraction and positive wave impedance is the correct one, and that this choice is consistent with the overall causality of the response. An analytical, exact frequency domain solution to the scattering of a wave from a DNG slab is also given and is used to characterize several physical effects. This solution is independent of the choice of the square roots for the index of refraction and the wave impedance, and thus avoids any controversy that may arise in connection with the signs of these constituents. The DNG slab solution is used to critically examine the perfect lens concept suggested recently by Pendry. It is shown that the perfect lens effect exists only under the special case of a DNG medium with $\ensuremath{\epsilon}(\ensuremath{\omega})=\ensuremath{\mu}(\ensuremath{\omega})=\ensuremath{-}1$ that is both lossless and nondispersive. Otherwise, the closed form solutions for the field structure reveal that the DNG slab converts an incident spherical wave into a localized beam field whose parameters depend on the values of $\ensuremath{\epsilon}$ and $\ensuremath{\mu}.$ This beam field is characterized with a paraxial approximation of the exact DNG slab solution. These monochromatic concepts are again explored numerically via a causal two-dimensional FDTD simulation of the scattering of a pulsed cylindrical wave by a matched, lossy Drude model DNG slab. These FDTD results demonstrate conclusively that the monochromatic electromagnetic power flow through the DNG slab is channeled into beams rather then being focused and, hence, the Pendry perfect lens effect is not realizable with any realistic metamaterial.

Microwave transmission through a two-dimensional, isotropic, left-handed metamaterial

Abstract: We present experimental data, numerical simulations, and analytical transfer-matrix calculations for a two-dimensionally isotropic, left-handed metamaterial (LHM) at X-band microwave frequencies. A LHM is one that has a frequency band with simultaneously negative eeff(ω) and μeff(ω), thereby having real values of index of refraction and wave vectors, and exhibiting extended wave propagation over that band. Our physical demonstration of a two-dimensional isotropic LHM will now permit experiments to verify some of the explicit predictions of reversed electromagnetic-wave properties including negative index of refraction as analyzed by Veselago [Usp. Fiz. Nauk 92, 517 (1964), Sov. Phys. Usp. 10, 509 (1968)].

Photonic Crystals and Light Localization in the 21st Century

Abstract: Preface. Group Picture. Photonic Crystals: Introduction. Novelties of Light With Photonic Crystals J.D. Joannopoulos, et al. 3D Photonic Crystals: From Microwaves to Optical Frequencies C.M. Soukoulis. Tunable Photonic Crystals K. Busch, S. John. Acoustic Band Gap Materials J.H. Page, et al. The Finite Difference Time Domain Method for the Study of Two-Dimensional Acoustic and Elastic Band Gap Materials M. Kafesaki, et al. Photonic Crystals: Fabrication and Application. Micro-Fabrication and Nano-Fabrication of Photonic Crystals S.Y. Lin, et al. Semiconductor Photonic Crystals S. Noda, et al. Light Propagation Characteristics of Defect Waveguides in a Photonic Crystal Slab T. Baba, N. Fukaya. Applications of Two-Dimensional Photonic Crystals to Semiconductor Optoelectronic Devices H. Benisty, et al. Patterned Photonic Crystal Waveguides T.F. Krauss. Photonic Crystals from Macroporous Silicon R.B. Wehrspohn, et al. Characterization of a Three-Dimensional Microwave Photonic Band-Gap Crystal J. Fagerstrom, et al. One-Dimensional Periodic Structures Under a New Light D.N. Chigrin, C.M. Sotomayor Torres. Defect Modes in Quasi-One-Dimensional Photonic Waveguides - Application to the Resonant Tunneling Between Two Continua J.O. Vasseur, et al. Photonic Crystals: Fabrication by Self Organization. Experimental Probes of the Optical Properties of Photonic Crystals W.L. Vos, et al. Inverse Opals Fabrication H. Miguez, et al. The Complete Photonic Band Gap in Inverted Opals: How can we prove it experimentally? D.J. Norris, Y.A. Vlasov. Manipulating Colloidal Crystallization for Photonic Applications: From Self-Organization To Do-It-Yourself Organization A.van Blaaderen, et al. Thin Opaline Photonic Crystals S.G. Romanov, et al. Tunable Shear-Ordered Face-Centered Cubic Photonic Crystals R.M. Amos, et al. Photonic Crystals: Applications. Physics and Applications of Photonic Crystals E. Ozbay, et al. Photonic Crystal Fibers: Effective-Index and Band-Gap Guidance D.C. Allan, et al. Applications of Photonic Crystals to Directional Antennas R. Biswas, et al. Photonic Crystals: Metallic Structures. Intense Focusing of Light Using Metals J.B. Pendry. Left-Handed Metamaterials D.R. Smith, et al. Towards Complete Photonic Band Gap Structures Below Infrared Wavelengths A. Moroz. Effect of Moderate Disorder on the Absorbance of Plasma Spheres Distributed in a Host Dielectric Medium V. Yannopapas, et al. Random Lasers. Random Lasers With Coherent Feedback H. Cao, et al. Analysis of Random Lasers in Thin Films of p-Conjugated Polymers R.C. Polson, et al. Theory and Simulations of Random Lasers X. Jiang, C.M. Soukoulis. Cavity Approach Towards a Coherent Random Lasers J.P. Woerdman, et al. Localization of Light. Propagation of Light in Disordered Semiconductor Materials A. Lagendijk, et al. Radiative Transfer of Localized Waves: A Local Diffusion Theory B.A. Van Tiggelen, et al. Dynamics of Localization in a Waveguide C.W.J. Beenakker. From Proximity Resonances to Anderson Localization A. Orlowski, M. Rusek. Photonic Crystals and Nonlinearities. Band-Structure and Transmittance Calculations for Phononic Crystals by the LKKR Method I.E. Psarobas, et al. Multipole Methods for Photonic Crystal Calculations N.A. Nicorovic

Superluminal transmission of information through an electromagnetic metamaterial.

Abstract: A passive, matched two-time-derivative Lorentz material medium is designed to have its equivalent permittivity and permeability smaller than their values in free space over a large range of frequencies. Superluminal pulse propagation in this medium and consequent superluminal information exchange without a violation in causality are demonstrated. Additional properties of this medium are developed including the energy in it and the force characteristics induced on it by electromagnetic field interactions. It is shown that the force on the medium can be made to be attractive or repulsive using a change in frequency or a change in the material characteristics. Potential applications are discussed.

Meta‐materials with wideband negative permittivity and permeability

Abstract: Recently, electromagnetic materials with negative permittivity and permeability values (sometime called “media with negative refraction index”) have been given much attention in the literature. Negative values of the material parameters can be achieved in composite media near resonances, which implies very dispersive properties. The material parameters are complex numbers to account for dissipation, and the real parts can be negative only in narrow frequency bands. Here, we show that this limitation can be relaxed in composite materials with active inclusions. It is proven that, using small dipole and loop antennas loaded by certain simple electronic circuits as composite inclusions, the material behaves as an effective medium with real negative parameters in wide frequency bands. Similarly, thin sheets of negative materials can be simulated by strip or patch arrays loaded by active circuits. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 163–165, 2001.

Ab initio numerical simulation of left-handed metamaterials: Comparison of calculations and experiments

Abstract: Using numerical simulation techniques, the transmission and reflection coefficients, or S parameters, for left-handed metamaterials are calculated. Metamaterials consist of a lattice of conducting, nonmagnetic elements that can be described by an effective magnetic permeability μeff and an effective electrical permittivity eeff, both of which can exhibit values not found in naturally occurring materials. Because the electromagnetic fields in conducting metamaterials can be localized to regions much smaller than the incident wavelength, it can be difficult to perform accurate numerical simulations. The metamaterials simulated here, for example, are based on arrays of split ring resonators (SRRs), which produce enhanced and highly localized electric fields within the gaps of the elements in response to applied time dependent fields. To obtain greater numerical accuracy we utilize the newly developed commercially available code MICROWAVE STUDIO, which is based on the finite integration technique with the per...

Two-dimensional photonic crystals: Candidate for wave plates

Abstract: We have numerically investigated the optical paths of S and P waves propagating through two-dimensional photonic crystals consisting of dielectric cylinders parallel to each other, where S waves and P waves specify electromagnetic waves with the electric field parallel to the cylinders and electromagnetic waves with the electric field perpendicular to the cylinders, respectively. It is found that the difference between the optical paths of S and P waves can be many times the path difference in the case of a conventional wave plate with the same thickness. Therefore, we propose that two-dimensional photonic crystals can be employed as thin wave plates that can be used as integrated optical and microwave components.

Step-like structure and EBG structure to improve the performance of patch antennas on high dielectric substrate

Abstract: Applications of microstrip antennas on high dielectric constant substrate are of growing interest due to their compact size and conformability with monolithic microwave integrated circuit (MMIC). However, there are some drawbacks with the use of high dielectric constant substrate such as narrow bandwidth, low efficiency and poor radiation patterns, which result from the pronounced excitation of surface waves. Several methods were previously used to overcome these drawbacks by manipulating the antenna substrate. One approach suggested was to lower the effective dielectric constant of substrate under the patch using micromachining techniques. A shortcoming of this approach is the larger patch size than that on the unperturbed substrate. Another approach is to surround the patch with a complete band-gap structure or synthesized low dielectric constant substrate so that the surface wave can be reduced. In this paper, a step-like substrate and electromagnetic band-gap (EBG) structure is applied to the patch antennas separately to overcome the undesirable features of the high dielectric constant substrate without sacrificing any of the desirable features, namely, small size and bandwidth. Both numerical and experimental results are presented to demonstrate the validity of these two approaches.

Left-Handed Metamaterials

Abstract: The response of a material to electromagnetic radiation can be entirely characterized by the material parameters: the electrical permittivity, or e, and the magnetic permeability, or μ. The range of possible values for the material parameters, as dictated by fundamental considerations such as causality or thermodynamics, extends beyond that found in naturally occurring materials. We thus seek to extend the material parameter space by creating electromagnetic metamaterials—ordered composite materials that display electromagnetic properties beyond those found in naturally occurring materials. Recently, we have demonstrated a metamaterial made of a repeated lattice of conducting, nonmagnetic elements that exhibits an effective μ and an effective e, both of which are simultaneously negative over a band of frequencies [1]. Such a medium has been termed Left-Handed [2], as the electric field (E), magnetic intensity (H) and propagation vector (k) are related by a left-hand rule. We introduce the reader to the expected properties predicted by Maxwell’s equations for Left-Handed media, and describe our recent numerical and experimental work in developing and analyzing this new metamaterial.