Metamaterials

This communication presents a novel technique for the analysis and design of complex antennas, including reflectoarrays and antennas composed by metamaterials and other finite-sized multilayered quasi-periodic structures. This method is based on the Method of Moments, and the combination of the Multilevel Fast Multipole Algorithm (MLFMA) [1] and the Characteristics Basis Function Method (CBFM) [2] has been applied to reduce the computational cost. The method has been tested considering several periodic structures achieving good results.

The acoustic transmission of a closely spaced pair of patterned and perforated rigid plates is explored in air. The structure resembles an acoustic double fishnet design, with each plate modified such that the gap between them acts as an array of Helmholtz resonators. This allows the center frequency of the stop band to be reduced by a factor greater than 2 from the value obtained for the conventional acoustic double fishnet design. Experimental results accord well with the predictions of a finite element model.

The development of metamaterials that possess desired optical properties over a spectral band is a
problem of fundamental importance; its solution could considerably improve the performance of
many existing optical devices and allow new devices. Dealing with nanostructured metal/dielectric
composites (subwavelength photonic crystals) with a specified spatial configuration, within the
framework of the effective medium theory, we obtain an approximation for their effective
permittivity. Then, making use of this approximation, we propose a scheme for designing above
metamaterials. As practically important particular examples, we consider quasi-one-dimensional
metamaterials with ultralow refractive index, a high absorption, and those possessing pass-band
filtering properties.

Motivated by the need for a multi-parameter sensing chip for water networks monitoring, we address here the specific case of a flow-rate sensor where the main challenge is the substrate material. Instead of using conventional low thermal conductivity materials such as glass, silicon has to be used. Indeed, a silicon substrate enables the co-integration of various kinds of sensors on the same chip as reported in this contribution. However, it increases the flow-rate sensor power consumption due to larger thermal leaks. We therefore design and study an optimized low power micro-machined thermal flow-rate sensor based on a silicon substrate and operating according to hot-wire anemometry. It can be considered as an alternative to other well established sensors for liquid flow-rate measurement when both the use of a silicon substrate and a low power consumption are needed.

A simple, compact, rechargeable handheld radio-frequency identifi cation (RFID) reader was designed to detect the orientation of tagged objects. The system uses a linearly polarized reader antenna and the orientation sensor of the mobile device to identify the orientation of the tag. The system works in the ultra-high-frequency (UHF) RFID band. Detailed testing was done in different surroundings with various materials and tags. The system was able to correctly identify the orientation in several cases with an average angular error of less than 10°. This system can also be used to demonstrate the concept of polarization.

The nonstationary parametric interaction of waves in negative-index metamaterials is studied in the second-order dispersion theory. A nonlinear interaction between a long pulse of a strong pump wave and an ultrashort pulse with quadratic phase modulation is considered. The results of calculating the shape of the spectrum of an excited signal wave are presented. A comparison is made with the case of interaction in an ordinary medium. It is shown that the effects of group-velocity dispersion and dispersive spreading in such materials lead to a narrowing of the spectrum of the excited wave. The presence of phase modulation of the exciting idler pulse promotes broadening of the central maximum of the spectrum of the excited signal wave. As the modulation factor increases, the fragmentation of the excited pulse is observed.

Coplanar waveguide (CPW) transmission lines periodically coupled to split-ring resonators (SRRs) are analyzed, designed, and characterized. Due to inductive coupling between the lines and SRRs, signal propagation is inhibited in the vicinity of the resonant frequency of the rings. The result is a stop-band behavior that can be of interest for the elimination of frequency parasitics in CPW-based devices. Two different approaches are envisaged: a uniplanar structure, where CPW and rings share the same metal level; and a bimetal structure with SRRs etched on the back side of the substrate. It has been found that the latter exhibits almost negligible insertion losses in the pass band, and sharp cutoff and a high level of rejection in the stop band, with few unit cells. Since ring dimensions are small compared to the signal wavelength at resonance, the proposed SRR-CPWs are very promising for the design of miniaturized microwave circuits. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 3–6, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11269

Metamaterials (MTM) have become a major electromagnetic research topic. Initial studies have focused on understanding their electromagnetic properties and interactions. This paper presents a novel virtual tool, MTM-FDTD, for the visualization of electromagnetic wave interacting with different metamaterials. Snapshots from characteristic examples during these interactions are presented. Scenarios with normal and oblique incidences, demonstrating focusing beams in planar metamaterials and

In this paper we list out root elements as per Vedic Metallurgy described in Vaimanika Prakarana of Bharadwaja . Root or Beeja Loha as they are called are , elements formed inside the earth during formation of earth’s crust & by influence of cosmic rays coming from Sun , Moon & other deep space objects . By using different combinations of these Beeja Lohas , different alloys are made which had advanced properties like heat absorbent, heat resistant  , light weight , cold resistant etc

The Drude-Lorentz model is a well-known method used to estimate the permittivity of a material, describing its atoms as oscillating dipoles. Notwithstanding its simplicity, in many contexts that model is quite effective and so today it's widely used. In this paper we are going to present a circuit model analogous to the Drude-Lorentz one and formally governed by the same harmonic equation. In order to better describe the atomic dipole, we also introduce the concept of half-capacitor, i.e. a circuit element allowing to accumulate net charge on a node. The resulting circuit is quite simple but easy to be extended in 3D and to multi-orbital atoms. However, it is primarily intended to be a powerful project tool for microscopic structures in the field of metamaterials.

A smart high Tc superconductor meta-material with off mass-shell near field resonances is predicted to behave like the exotic matter needed for weightless geodesic warp drive as well as for the wormhole time machines depicted in Kip Thorne's movie "Interstellar."

This paper presents a microwave sensor for simultaneous measurement of permittivity and thickness in dielectric materials. The sensor is made of a dual-mode magnetic-LC resonator coupled to a microstrip transmission line. Due to a dual-mode resonance of the magnetic-LC res-onator, the transmission response of the sensor shows two zero frequencies. By applying dielectric materials of various permittivities and thicknesses to the resonator, both of the transmission zero frequencies are modified. The alterations of the two transmission zero frequencies are used to characterize the permittivity and thickness of the dielectric samples under test. A prototype of the sensor is fabricated and measured for verifying the proposed sensing principle.

Design of wideband Substrate Integrated
Waveguide (SIW) filter operable in Ku-band has been
presented in this paper. Single and multiple stepped
Inductive posts have been used for obtaining the bandpass
characteristics. The pass-band shows transmission
characteristics from 12GHz to 17.5GHz. The filter is fed
using microstrip to SIW transition technique over a material
with dielectric constant of 3.48 and thickness of
0.51mm. Several Array alignments of inductive posts
have been analyzed and the effects have been produced
in this article. The design comes with minimal insertion
loss over the entire bandwidth.

During the recent years by climate changes, Perspolis and Pasargad are suffering hard conditions of weathering damages and also lack of proper preservation. The crystallization of soluble salts is the most aggressive physical and chemical process. As a contribution to monument preservation, the aim of this paper is to provide a mathematical simulation by finite elements method (F.E.M) to find out effects of weathering damages and predict the responses of different methods of conservations, for different problems such as: 1) weathering, 2) differential settlement, 3) erthquake. Numerical simulation of problems and the intelligent solutions (details) related to historical building are our outcome. ABAQUS and ANSYS software and Druger-Prager constitutive equation model are the tools which are used in the paper. First results on the computational assessment compare with visual damages of structures in both site shows reasonable verifications.

In this paper, microstrip lines magnetically coupled to split-ring resonators (SRRs) are compared to electromagnetic bandgap (EBG) microstrip lines in terms of their stop-band performance and dimensions. In both types of transmission lines, signal propagation is inhibited in a certain frequency band. For EBG microstrip lines, the central frequency of such a forbidden band is determined by the period of the structure, whereas in SRR-based microstrip lines the position of the frequency gap depends on the quasi-static resonant frequency of the rings. The main relevant contribution of this paper is to provide a tuning procedure to control the gap width in SRR microstrip lines, and to show that by using SRRs, device dimensions are much smaller than those required by EBGs in order to obtain similar stop-band performance. This has been demonstrated by full-wave electromagnetic simulations and experimentally verified from the characterization of two fabricated microstrip lines: one with rectangular SRRs etched on the upper substrate side, and the other with a periodic perturbation of strip width. For similar rejection and 1-GHz gap width centered at 4.5 GHz, it has been found that the SRR microstrip line is five times shorter. In addition, no ripple is appreciable in the allowed band for the SRR-based structure, whereas due to dispersion, certain mismatch is expected in the EBG prototype. Due to the high-frequency selectivity, controllable gap width, and small dimensions, it is believed that SRR coupled to planar transmission lines can have an actual impact on the design of stop-band filters compatible with planar technology, and can be an alternative to present solutions based on distributed approaches or EBG. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 376–379, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20640

We extend the design of radially symmetric three-dimensional invisibility cloaks through transformation optics to cloaks with a surface of revolution. We derive the expression of the transformation matrix and show that one of its eigenvalues vanishes on the inner boundary of the cloaks, while the other two remain strictly positive and bounded. The validity of our approach is confirmed by finite edge-elements computations for a non-convex cloak of varying thickness.

We present the utilization finite
element method as implemented in COMSOL
Multiphysics for understanding three different
types of wave guidance mechanisms in photonic
crystal fibers (PCFs), like modified total internal
reflection, Bragg’s reflection and resonant
trapping of defect mode at Dirac frequency.
Effective refractive indices of the core and
cladding are calculated using mode analysis
study to verify total internal reflection in a solid
core PCF. The photonic band structure (PBS) of
the cladding is calculated using eigen frequency
study to identify photonic band gap region which
constitute the transmission window of a hollow
core PCF. The eigen frequency of the Dirac point
is identified from the PBS. Trapping of Dirac
mode is obtained by optimizing the defect radius
in such a way that the defect state resonate at the
Dirac frequency. This study is important for
designing and investigating the performance of
various PCF based devices for advanced
applications.

This paper presents a method for calculating the
Zernike aberrations in a lens design using transformation optics
in FDTD. Currently there is no literature on calculating image
aberrations in FDTD. In this paper I divulge the methods to
calculate the Zernike aberration using a polynomial fitting for
a wavefront. The results are shown to match very well with the
Zernike aberrations in an equivalent lens in ZEMAX.

The mechanical behaviour of microstructured materials is attracting considerable research interest, from both the academic and the industrial communities.
The phenomenon of wave propagation through these media and its implications are in particularly explored.
The pertinent mathematical techniques are first discussed and several test cases of increasing complexity are illustrated.
The dispersion relations, the phase and the group velocities are derived both in a second and in a micromorphic approach and the main advantages of these models are analysed.
The peculiar phenomenon of localisation is also investigated with regards to damaged materials which exhibit a degradation of their mechanical properties. A simple FEM code, implemented for the study of the wave propagation in a one-dimensional domain, is presented together with an accurate validation. Some simulations are then run with this software and the outputs are compared with the analytical results previously obtained.

— This paper presents a microwave sensor using a pair of split-ring resonators (SRRs). The sensor is designed by loading a microstrip transmission line by two identical SRRs on its sides. Differential permittivity sensing is performed by loading the SRRs with dielectric samples. One transmission notch is observed for the identical loads, whereas the non-identical samples produce two split notches. The sensor's operating principle is described through a circuit model analysis. A prototype of the designed sensor is fabricated and experimentally validated for verifying the differential sensing concept. The developed device can be used to compare or differentially characterize solid dielectric samples improving the robustness to environmental factors producing cross-sensitivity or miscalibration.

This work contains the comprehensive work of my PhD. Contained in background to invisibility cloaking and carpet cloaking. My contribution to the design of a transformation optics inspired Cooke Triplet with low aberrations. The quantitative analysis of the Zernike aberrations due to the wavefront aberration. A comparison with conventional commercial design software Zemax.

A meander stripline feed multiband microstrip antenna loaded with metasurface reflector (MSR) structure has been designed, analyzed and constructed that offers the wireless communication services for UHF/microwave RFID and WLAN/WiMAX applications. The proposed MSR assimilated antenna comprises planar straight forward design of circular shaped radiator with horizontal slots on it and 2D metasurface formed by the periodic square metallic element that resembles the behavior of metamaterials. A custom made high dielectric bio-plastic substrate (epsilon(r) = 15) is used for fabricating the prototype of the MSR embedded planar monopole antenna. The details of the design progress through numerical simulations and experimental results are presented and discussed accordingly. The measured impedance bandwidth, radiation patterns and gain of the proposed MSR integrated antenna are compared with the obtained results from numerical simulation, and a good compliance can be observed between them. The investigation shows that utilization of MSR structure has significantly broadened the -10dB impedance bandwidth than the conventional patch antenna: from 540 to 632 MHz (17%), 467 to 606 MHz (29%) and 758 MHz to 1062 MHz (40%) for three distinct operating bands centered at 0.9, 3.5 and 5.5 GHz. Additionally, due to the assimilation of MSR, the overall realized gains have been upgraded to a higher value of 3.62 dBi, 6.09 dBi and 8.6 dBi for lower, middle and upper frequency band respectively. The measured radiation patterns, impedance bandwidths (S11<-10 dB) and gains from the MSR loaded antenna prototype exhibit reasonable characteristics that can satisfy the requirements of UHF/microwave (5.8 GHz) RFID, WiMAX (3.5/5.5 GHz) and WLAN (5.2/5.8 GHz) applications.

Link to full text journal article :
http://www.ncbi.nlm.nih.gov/pubmed/26018795
http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0127185&representation=PDF

With conventional narrowband filters, the center-wavelength of the narrow transmission band undergoes large shifts as the angle of incident light changes. In this project, we designed and experimentally verified a type of hyperbolic metamaterial Bragg stack that eliminates, or vastly reduces, this angle-of-incidence dependence (i.e., dispersion) of the transmission band for TM polarized beam. The filter developed in this project is composed of array of subwavelength sized metal wires vertically penetrating in the dielectric layers of the Bragg stack. We first discuss the physical reasons why such a structure is expected to minimize dispersion, then we performed detailed electromagnetic modeling, fabrication of proof-of-concept structures, and optical testing of the structures. The filter is fabricated by CMOS fabrication techniques at Cornell University’s Nanoscale Science and Technology Center, and optical characterized using Fourier-transform infrared spectroscopy. Both simulated and experimental data show that narrow band transmission filters can be designed such that the center-wavelength of the transmission peak for TM polarized incident light does not change as the angle of incidence of an incoming beam changes. These types of narrowband notch filters have been used in many sensing and imaging applications, including remote sensing and hyperspectral imaging.

Metamaterials are artificial composites that acquire their electromagnetic properties from embedded subwavelength metallic structures. In theory, the effective electromagnetic properties of metamaterials at any frequency can be engineered to take on arbitrary values, including those not appearing in nature. As a result, this new class of materials can dramatically add a degree of freedom to the control of electromagnetic waves.
The emergence of metamaterials fortunately coincides with the intense emerging interest in terahertz radiation (T-rays), for which efficient forms of electromagnetic manipulation are sought. Considering the scarcity of naturally existing materials that can control terahertz, metamaterials become ideal substitutes that promise advances in terahertz research. Ultimately, terahertz metamaterials will lead to scientific and technological advantages in a number of areas. This article covers the principles of metamaterials and reviews the latest trends in terahertz metamaterial research from the fabrication and characterization to the implementation.

This study investigates ultra-thin transparent conducting oxides (TCO) of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO) and zinc oxide (ZnO) to determine their viability as candidate materials for use in plasmonic-enhanced thin-film amorphous silicon solar photovoltaic (PV) devices. First a sensitivity analysis of the optical absorption for the intrinsic layer of a nano-disk patterned thin-film amorphous silicon-based solar cell as a function of TCO thickness (10–50 nm) was performed by simulation. These simulation results were then used to guide the design of the experimental work which investigated both optical and electrical properties of ultra-thin (10 nm on average) films simultaneously deposited on both glass and silicon substrates using conventional rf sputtering. The effects of deposition and post-processing parameters on material properties of ITO, AZO and ZnO ultra-thin TCOs were probed and the suitability of TCOs for integration into plasmonic-enhanced thin-film solar PV devices was assessed. The results show that ultra-thin TCOs present a number of challenges for use as thin top contacts on plasmonic-enhanced PV devices: (1) optical and electrical parameters differ greatly from those of thicker (bulk) films deposited under the same conditions, (2) the films are delicate due to their thickness, requiring very long annealing times to prevent cracking, and (3) reactive gases require careful monitoring to maintain stoichiometry. The results presented here found a trade-off between conductivity and transparency of the deposited films. Although the sub 50 nm TCO films investigated exhibited desirable optical properties (transmittance greater than 80 %), their resistivity was too high to be considered as materials for the top contact of conventional PV devices. Future work is necessary to improve thin TCO properties, or alternative materials, and geometries are needed in plasmonic-based amorphous silicon solar cells. The stability of ultra-thin TCO films also needs to be experimentally investigated under normal device operating conditions.

Discovery finds its roots in a desire to investigate the unknown. This notion of discovery defines the very interaction man has with nature; airplanes have sought to be the new birds, submarines have plunged deeper than any whale and solar cells have become the rightful heirs of plants. What happens though when discovery pertains to a system never before observed? When science is not content in merely imitating nature, it goes ‘beyond’ nature, inventing its own ‘meta’ realm.
In this paper, a brief history of metamaterial research will act as a preface to a more detailed analysis of optical metamaterials and their shortcomings, highlighting the major issues when trying to find practical implementations when approaching visible wavelengths. Solutions to problems such as losses and instability are suggested via the introduction of gold nanoparticles coated with organic aliphatic chains in Liquid Crystal devices; these structures act as precursors to creating tailor-made metamaterial structures and show much promise in a diverse range of fields due to their versatility.

This is a short introduction to metamaterials. Guiding the reader through the key innovations provided by the technology of invisibility cloaks and sub length imaging devices. Additional aspects of physics which are touched on include table top astronomical devices, optics and materials science.

An insightful mechanics-based bottom-up framework is developed for probing the frequency-dependence of lattice material microstructures. Under a vibrating condition, effective elastic moduli of such microstructured materials can become negative for certain frequency values, leading to an unusual mechanical behaviour with a multitude of potential applications. We have derived the fundamental theoretical limits for the minimum frequency, beyond which the negative effective moduli of the materials could be obtained. An efficient dynamic stiffness matrix based approach is developed to obtain the closed-form limits, which can exactly capture the sub-wavelength scale dynamics. The limits turn out to be a fundamental property of the lattice materials and depend on certain material and geometric parameters of the lattice in a unique manner. An explicit characterization of the theoretical limits of negative elastic moduli along with adequate physical insights would accelerate the process of its potential exploitation in various engineered materials and structural systems under dynamic regime across the length-scales. Introduction.-The global mechanical properties can be engineered in lattice materials by intelligently identifying the material microstructures as the properties in these materials are often defined by their structural configuration along with the intrinsic material properties of the constituent members. This novel class of materials with tailorable application-specific mechanical properties (like equivalent elastic moduli, buckling, vibration and wave propagation characteristics with modulation features) have tremendous potential applications for future aerospace, civil, mechanical, electronics and medical applications across the length-scales. Naturally occurring materials cannot exhibit unprecedented and fascinating properties such as extremely lightweight, negative elastic moduli, negative mass density, pentamode material characteristics (meta-fluid), which can be achieved by an intelligent microstructural design [1, 2]. For example, the conventional positive value of Poisson's ratio in a hexagonal lattice metamaterial can be converted to a negative value [3] by making the cell angle θ in figure 1(b) negative. Other unusual and exciting properties can be realized in metamaterials under dynamic condition, such as negative bulk modulus induced by monopolar resonance [4], negative mass density induced by dipolar resonance [5], and negative shear modulus induced by quadrupolar resonance [6]. Elastic cloaks [7] and various other unprecedented dynamic behaviour of such materials have been widely reported in literature [8-14].