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Metamaterials
Selected AbstractsFabrication of a novel micron scale Y-structure-based chiral metamaterial: Simulation and experimental analysis of its chiral and negative index properties in the terahertz and microwave regimesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2007Nantakan Wongkasem Abstract In this report, we describe the fabrication of a chiral metamaterial based on a periodic array of Y-shaped Al structures on a dielectric Mylar substrate. The unit cell dimensions of the Y-structure are ,100 ,m on a side with 8 ,m linewidths. The fabricated Y-structure elements are characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative elemental analyses were carried out on both the Y-structure, comprised of Al and its oxide, as well as adjacent regions of the underlying mylar substrate using the energy dispersive X-ray spectroscopy (EDS) capability of the SEM. Finite-Difference Time-Domain (FDTD) calculations of the negative index of refraction for a 3D wedge of multiple layers of the 2D metamaterials showed that these metamaterials possess double negative (,,,,,) electromagnetic bulk properties at THz frequencies. The same negative index of refraction was determined for a wedge comprised of appropriately scaled larger Y-structures simulated in the microwave region. This double negative property was confirmed experimentally by microwave measurements on a 3D wedge comprised of stacked and registered Y-structure sheets. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Filter design and mode suppression inside metamaterial-filled rectangular waveguidesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Sibel Çimen Abstract Filter characteristics and mode suppression capabilities inside metamaterial- (MTM) filled rectangular waveguides are investigated. Frequency characteristics of single-negative (SNG) and double-negative (DNG) finite slength transverse slabs inside rectangular waveguides are numerically simulated. The simulations are performed via in-house-prepared three-dimensional (3D) finite-difference time-domain package; MTM-3D. Simulations are also repeated with the commercial CST Microwave Studio package and results are compared. Tests show that different combinations of SNG and DNG slabs located transversely inside a rectangular waveguide can be used to obtain multi-stopband filters and to suppress modes (i.e., resonances). © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1659,1663, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25289 [source] Gain-assisted metamaterial embedded with gain elementsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010Tao Jiang Abstract In this letter, an active metamaterial sample embedded with miniature monolithic microwave amplifiers is designed, experimentally realized, and measured. Experiments show that by proper design and direct current (DC) bias, the metamaterial sample provides almost linear amplification to an electromagnetic incidence, which can be used to compensate the loss inherent in traditional passive metamaterial and magnify the signal entered the metamaterial. This property would have important potentials in promoting the further researches of metamaterial-based applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 92,95, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24871 [source] Meta-structured one-unit-cell epsilon negative antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009Seongnam Jang Abstract This Letter presents a metamaterial-based compact one-unit-cell epsilon negative zeroth-order resonant antenna designed on a microstrip line. The size of the proposed antenna is only 7.85 mm × 18 mm (or 0.05,0 × 0.12,0) at 1.79 GHz owing to zeroth-order resonance. Closed-form design equations for the proposed antenna are provided based on the equivalent circuit employing transmission line theory considering radiation loss. The return losses based on circuit/EM simulations and measurement are in excellent agreement. The measured antenna bandwidth is 17 MHz (about 1%) and total gain is 2.6 dBi. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2991,2994, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24751 [source] Cylindrical metamaterial-based subwavelength antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009Aycan Erentok Abstract A subwavelength monopole antenna radiating in the presence of a truncated cylindrical shell, which has a capped top face and is made of a negative permittivity metamaterial, is analyzed numerically by a method of moments for the volume-surface integral equation on the one hand, and a finite element method on the other hand. It is shown that a center-fed truncated cylinder, in contrast to an infinite cylinder, provides subwavelength resonances, thus suggesting the possibility of having a subwavelength antenna system. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1496,1500, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24386 [source] A directive dual-band and dual-polarized antenna with zero index metamaterialMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008Zi-Bin Weng Abstract A novel directive dual-band and dual-polarized microstrip antenna with ZIM is presented. An averaging effect over constituent materials of the metamaterial structure yields an effective permittivity that approaches zero at dual band with different polarizations, and then it results in a metamaterial with zero index of refraction and the radiation energy of this antenna is congregated. The experimental results show that this method is effective, and this structure can greatly increase the gain at dual frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2902,2904, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23855 [source] A directive patch antenna with metamaterial structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007Zi-bin Weng Abstract A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice is presented. The influences of the number of metamaterial layers and a comparison of electromagnetic characteristics between the conventional patch antenna and the new metamaterial patch antenna are studied by using numerical simulation method. Then, a patch antenna with the metamaterial is fabricated and measured. The simulation and experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gain of the antenna with metamaterial can greatly increase when compared with the conventional one. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 456,459, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22146 [source] Optimization of metamaterial based subwavelength cavities for ultracompact directive antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2006A. Ourir Abstract Artificial magnetic conductors (AMC) are proposed for the fabrication of subwavelength cavities in the microstrip technology. These metamaterials can simultaneously present a low phase value at reflection and a high impedance for normal incident waves over a wide frequency band. Planar cavities using AMC-based reflectors are applicable to the design of ultracompact directive antennas. An optimized cavity structure is presently shown to provide a significant enhancement of the gain and directivity of a microstrip antenna near 10 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2573,2577, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21996 [source] Experimental investigation of radiation properties of an antenna embedded in low permittivity thin-wire-based metamaterialMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2006Davor Bonefa Abstract Experimental results regarding the increase in directivity and gain of an antenna embedded in low-permittivity two-dimensional anisotropic thin-wire-based metamaterial are presented. As expected, increase in directivity and gain has been observed. The effect of main beam splitting with frequency increase, predicted by theoretical analysis, has been confirmed. The influence of the number of layers forming the metamaterial on the radiation pattern and gain has been investigated. Input impedance was measured both as a function of frequency and of the number of wire layers forming the metamaterial. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2581,2586, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21994 [source] Design and double negative property verification of C band left-handed metamaterialMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2006Fan-Yi Meng Abstract In this article, a left-handed (LH) metamaterial with miniaturized unit cell and broad bandwidth is designed. Its relative bandwidth is 56.4%, and the unit cell electrical size is 0.067 at the central frequency where the LH metamaterial is available. The effective permittivity and effective permeability are extracted from the transmission and reflection data at normal incidence for the LH metamaterial proposed here. The double negative (DNG) property is shown by the simultaneously negative effective permittivity and effective permeability and is confirmed by the equivalent circuit. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1732,1736, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21763 [source] Negative permeability around 630 nm in nanofabricated vertical meander metamaterialsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2007Heinz Schweizer Abstract We demonstrate a new design of a 3-dimensional meander structure that exhibits negative permeability with a broad bandwidth between 550 nm and 665 nm. The structural design allows for full coupling of the magnetic field component at all angles of incidence. We compare our structure with other metamaterial structures with respect to the series capacitance contributions of the different metamaterials. The investigation of optical metamaterials is carried out combining transmission line analysis with numerical simulations of Maxwell's equations. The analysis is demonstrated for typical split ring structures and the novel 3D meander metamaterial structures. Comparing the resulting scattering parameter spectra as well as the retrieved effective material parameters, we find that transmission line description remains valid for metamaterials at optical frequencies. We find in addition that the longitudinal capacitance is the decisive parameter to achieve negative permeability with a broad bandwidth at optical frequencies. For experimental verification we manufactured split-ring resonator structures and meander metamaterial structures with linewidths down to 30 nm, element sizes down to 100 nm, and periods between 200 nm and 350 nm. For meander metamaterial structures a permeability value of ,1 was achieved within a bandwidth of 50 nm centered at 630 nm. The largest absolute value of ,4.5 was achieved at 650 nm. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] s-polarization Brewster's angle of stratified metal,dielectric metamaterial in optical regimePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2008Ryosuke Watanabe Abstract We demonstrate that the optical reflectivity for s-polarized light vanishes at a certain angle in a stratified metal,dielectric metamaterial numerically and experimentally. The metamaterial consists of a unit cell where a Ag layer of 30 nm thickness is sandwiched by Al2O3 layers of 60 nm thickness. In order to understand the phenomenon in terms of effective permittivity and permeability, we extended a field-sampling method. The permeability is found to be significantly different from unity, which is the origin of Brewster's angle for s-polarization. The microscopic field distribution is readily coarse grained with the effective optical parameters. The present result is a manifestation of the magnetic response in the optical regime. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnifying Superlenses and other Applications of Plasmonic Metamaterials in Microscopy and SensingCHEMPHYSCHEM, Issue 4 2009Igor I. Smolyaninov Dr. Abstract Every last detail: New advances in the construction of metamaterials enable the creation of artificial optical media, whose use in microscopy can provide resolution that is not determined by the conventional diffraction limit. The picture shows a superposition of an AFM image of a plasmonic metamaterial onto the corresponding optical image obtained using a conventional optical microscope. Over the past century, the resolution of conventional optical microscopes, which rely on optical waves that propagate into the far field, has been limited because of diffraction to a value of the order of a half-wavelength (,0/2) of the light used. Although immersion microscopes have slightly improved resolution, of the order of ,0/2n, the increased resolution is limited by the small range of refractive indices n of available transparent materials. However, now we are experiencing a quick demolition of the diffraction limit in optical microscopy. In the last few years, numerous nonlinear optical microscopy techniques based on photoswitching and saturation of fluorescence have demonstrated far-field resolution of 20 to 30 nm. In a parallel development, recent progress in metamaterials has demonstrated that artificial optical media can be created, whose use in microscopy can provide resolution that is not determined by the conventional diffraction limit. The resolution of linear immersion microscopes based on such metamaterials is only limited by losses, which can be minimized by appropriate selection of the constituents of the metamaterials used and by the wavelength(s) used for imaging. It is also feasible to compensate for losses by adding gain to the structure. Thus, optical microscopy is quickly moving towards resolution of around 10 nm, which should bring about numerous revolutionary advances in lithography and imaging. [source] Metamaterials: How Far Are We from Making Metamaterials by Self-Organization?ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010The Microstructure of Highly Anisotropic Particles with an SRR-Like Geometry (Adv. Funct. As part of ongoing efforts to create metamaterials by engineered self-organization using solidification of eutectics, D. A. Pawlak et al. report on page 1116 the fabrication of a fractal material with split-tubes mimicking (in cross section) the famous split-ring resonators (SRRs). The latter, when made of metal, are the basic element of a structure showing negative refractive index. This article shows that metallo-dielectric structures can be fabricated. The method employed has high potential for manufacturing materials with various functionalities. [source] How Far Are We from Making Metamaterials by Self-Organization?ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010The Microstructure of Highly Anisotropic Particles with an SRR-Like Geometry Abstract Metamaterials offer new unusual electromagnetic properties, which have already been demonstrated, and many postulated new functionalities are yet to be realized. Currently, however, metamaterials are mostly limited by narrow band behavior, high losses, and limitation in making genuinely 3D materials. In order to overcome these problems an overlap between metamaterial concepts and materials science is necessary. Engineered self-organization is presented as a future approach to metamaterial manufacturing. Using directional solidification of eutectics, the first experimental realization of self-organized particles with a split-ring resonator-like cross section is demonstrated. This unusual morphology/microstructure of the eutectic composite has a fractal character. With the use of TEM and XRD the clear influence of the atomic crystal arrangement on the microstructure geometry is presented. The materials obtained present very high anisotropy and can be obtained in large pieces. Metallodielectric structures can be created by etching and filling the space with metal. The next steps in the development of self-organized materials exhibiting unusual properties are discussed. [source] Spatial Patterning of the , -Phase in Poly(9,9-dioctylfluorene): A Metamaterials-Inspired Molecular Conformation Approach to the Fabrication of Polymer Semiconductor Optical StructuresADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Gihan Ryu Abstract Materials in which sub-wavelength physical structures, rather than variations in chemical composition, are used to modify the nature of their interaction with electromagnetic radiation form the promising new class of metamaterials. For molecular materials one has an intriguing alternative, namely structuring the conformation or physical geometry of the molecule. In order for this to be an effective methodology one needs the change in conformation i) to engender a significant change in electromagnetic properties and ii) to be spatially controllable to allow patterning of practical structures. In this paper the potential of such an approach is demonstrated through spatial patterning, via masked solvent vapor exposure, of the , -phase conformation in poly(9,9-dioctylfluorene) (PFO). Significantly the conformation change approach preserves a planar film format and is found not to negatively impact on optical gain properties, both very attractive features for optoelectronic and photonic lightwave circuit applications. As a specific demonstration the ability to spatially control the lasing wavelength for samples in which a , -phase conformation is selectively patterned in a glassy PFO film spin coated atop a one-dimensional distributed-feedback grating etched into a spectrosil substrate is shown. [source] Scalable Cylindrical Metallodielectric MetamaterialsADVANCED MATERIALS, Issue 38-39 2009Nicholas Gibbons A novel approach for fabricating metallodielectric metamaterials is reported through the exploitation of a floated roll technique. This process offers an efficient and scalable fabrication route for these multilayer structures, obviating the need for multiple depositions. These nanostructures can offer exciting new optical properties such as negative refraction and sub-wavelength imaging. [source] Magnonics: Spin Waves on the NanoscaleADVANCED MATERIALS, Issue 28 2009Sebastian Neusser Abstract Magnetic nanostructures have long been in the focus of intense research in the magnetic storage industry. For data storage the nonvolatility of magnetic states is of utmost relevance. As information technology generates the need for higher and higher data-transfer rates, research efforts have moved to understand magnetization dynamics. Here, spin waves and their particle-like analog, magnons, are increasingly attracting interest. High-quality nanopatterned magnetic media now offer new ways to transmit and process information without moving electrical charges. This new functionality is enabled by spin waves. They are confined by novel functioning principles, which render them especially suitable to operate at the nanoscale. Magnonic crystals are expected to provide full control of spin waves, similarly to what photonic crystals already do for light. Combined with nonvolatility, multifunctional metamaterials might be formed. We report recent advances in this rapidly increasing research field called magnonics. [source] Ordered Gold Nanoarrays: 3D Ordered Gold Strings by Coating Nanoparticles with Mesogens (Adv. Mater.ADVANCED MATERIALS, Issue 17 200917/2009) Liquid-crystal-coated gold nanoparticles exhibit 3D long-range ordering in strings jacketed by rod-like mesogens (shown in green) with controllable interparticle spacing. The work reported on p. 1746 by Goran Ungar and co-workers demonstrates a new method of assembling ordered metal nanoparticle superlattices, in a step towards developing self-assembled metamaterials. The cover shows red, yellow, and blue nanoparticles lying at different heights and forming a rhombohedral lattice. [source] Two-dimensional metamaterial opticsLASER PHYSICS LETTERS, Issue 4 2010I.I. Smolyaninov Abstract While three-dimensional photonic metamaterials are difficult to fabricate, many new concepts and ideas in the metamaterial optics can be realized in two spatial dimensions using planar optics of surface plasmon polaritons. In this paper we review recent progress in this direction. Two-dimensional photonic crystals, hyperbolic metamaterials, and plasmonic focusing devices are demonstrated and used in novel microscopy and waveguiding schemes. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Fabrication of a novel micron scale Y-structure-based chiral metamaterial: Simulation and experimental analysis of its chiral and negative index properties in the terahertz and microwave regimesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2007Nantakan Wongkasem Abstract In this report, we describe the fabrication of a chiral metamaterial based on a periodic array of Y-shaped Al structures on a dielectric Mylar substrate. The unit cell dimensions of the Y-structure are ,100 ,m on a side with 8 ,m linewidths. The fabricated Y-structure elements are characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative elemental analyses were carried out on both the Y-structure, comprised of Al and its oxide, as well as adjacent regions of the underlying mylar substrate using the energy dispersive X-ray spectroscopy (EDS) capability of the SEM. Finite-Difference Time-Domain (FDTD) calculations of the negative index of refraction for a 3D wedge of multiple layers of the 2D metamaterials showed that these metamaterials possess double negative (,,,,,) electromagnetic bulk properties at THz frequencies. The same negative index of refraction was determined for a wedge comprised of appropriately scaled larger Y-structures simulated in the microwave region. This double negative property was confirmed experimentally by microwave measurements on a 3D wedge comprised of stacked and registered Y-structure sheets. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Analysis of the double negative metamaterials using FDTDMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008Jia-Hui Fu Abstract Using the finite-difference time-domain method models ideal Drude of DNG metamaterials. The Z-transform is applied to model the Drude model that materials characterized by frequency dispersive behavior. Thus, we certificate the DNG metamaterials and its unique characteristics such as negative refraction, convergence, back-wave, phase compensation and verify the existence of DNG Metamaterials. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1411,1414, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23371 [source] Exploring the possibility of enhancing the bandwidth of ,-negative metamaterials by employing tunable varactorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007Andrea Alù Abstract We analyze here the performance of ,-negative metamaterials in different configurations at microwave and optical frequencies that employ variable values of capacitances or tunable varactors, with the purpose of increasing their bandwidth of operation. The proposed method shows moderately good results both in resonant-like and in transmission-line configurations. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 55,59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22036 [source] Further comments on the performances of finite element simulators for the solution of electromagnetic problems involving metamaterialsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2006Gaia Cevini Abstract In this paper, we analyze the performances of three-dimensional finite element (FE) simulators in handling electromagnetic scattering problems involving metamaterials. It has already been proved that the performances of the FE method are worse than usual, when metamaterials are considered. In this work, we extend our previous analysis by providing some additional results on the precision of the FE solution and on the performances of the iterative and direct solvers typically used with FE simulators. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2524,2529, 2006; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22008 [source] Optimization of metamaterial based subwavelength cavities for ultracompact directive antennasMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2006A. Ourir Abstract Artificial magnetic conductors (AMC) are proposed for the fabrication of subwavelength cavities in the microstrip technology. These metamaterials can simultaneously present a low phase value at reflection and a high impedance for normal incident waves over a wide frequency band. Planar cavities using AMC-based reflectors are applicable to the design of ultracompact directive antennas. An optimized cavity structure is presently shown to provide a significant enhancement of the gain and directivity of a microstrip antenna near 10 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2573,2577, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21996 [source] Effective constitutive parameters of structured chiral metamaterialsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2006O. Ouchetto Abstract In this paper we present a novel procedure for predicting the effective constitutive parameters of three-dimensional periodic materials with chiral component phases. The method combines the mathematical homogenization technique and the finite element method. The homogenization is accomplished by solving a local problem in the unit cell. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1884,1886, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21795 [source] Novel microstrip backward coupler with metamaterial cells for fully planar fabrication techniquesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2006E. Jarauta Abstract By using a recently proposed approach to synthesize 1D metamaterials in planar circuit technology, compatible with fully planar fabrication techniques, a novel backward coupler has been designed and fabricated. It has been implemented in microstrip technology by means of complementary split-ring resonators (CSRRs), etched in the ground plane, and series capacitive gaps. This way, we obtain the necessary left-handed properties for reversing the forward coupling (typical of co-directional coupled-line couplers) into backward coupling. The simulation as well as measurement results confirm the enhanced properties of the proposed couplers. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1205,1209, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21579 [source] Genetically engineered multiband high-impedance frequency selective surfacesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2003Douglas J. Kern Abstract A methodology is presented for the design synthesis of metamaterials that act as thin multifrequency artificial magnetic conductors. These structures are realized by placing a frequency-selective surface above a conventional prefect electric conductor, separated by a thin dielectric layer. The frequency-selective surface design is optimized using a micro-genetic algorithm to operate at multiple, narrow frequency bands. Two examples of genetically engineered multiband high-impedance frequency-selective surfaces (that is, artificial magnetic conductors) are presented and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 400,403, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11073 [source] A genetic algorithm approach to the design of ultra-thin electromagnetic bandgap absorbersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2003D. J. Kern Abstract A design methodology is presented for utilizing electromagnetic bandgap metamaterials, also known as artificial magnetic conductors, to realize ultra-thin absorbers. One approach that has recently been proposed is to place a resistive sheet in close proximity to a frequency-selective surface acting as an artificial magnetic conductor. However, we demonstrate in this paper that incorporating the loss directly into the frequency selective-surface can eliminate the additional resistive sheet, thereby further reducing the overall thickness of the absorber. The geometrical structure and corresponding resistance of this lossy frequency-selective surface is optimized by using a genetic algorithm to achieve the thinnest possible absorber. Two examples of genetically engineered electromagnetic bandgap metamaterial absorbers are presented and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 61,64, 2003 [source] Negative permeability around 630 nm in nanofabricated vertical meander metamaterialsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2007Heinz Schweizer Abstract We demonstrate a new design of a 3-dimensional meander structure that exhibits negative permeability with a broad bandwidth between 550 nm and 665 nm. The structural design allows for full coupling of the magnetic field component at all angles of incidence. We compare our structure with other metamaterial structures with respect to the series capacitance contributions of the different metamaterials. The investigation of optical metamaterials is carried out combining transmission line analysis with numerical simulations of Maxwell's equations. The analysis is demonstrated for typical split ring structures and the novel 3D meander metamaterial structures. Comparing the resulting scattering parameter spectra as well as the retrieved effective material parameters, we find that transmission line description remains valid for metamaterials at optical frequencies. We find in addition that the longitudinal capacitance is the decisive parameter to achieve negative permeability with a broad bandwidth at optical frequencies. For experimental verification we manufactured split-ring resonator structures and meander metamaterial structures with linewidths down to 30 nm, element sizes down to 100 nm, and periods between 200 nm and 350 nm. For meander metamaterial structures a permeability value of ,1 was achieved within a bandwidth of 50 nm centered at 630 nm. The largest absolute value of ,4.5 was achieved at 650 nm. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||