The Experts below are selected from a list of 21522 Experts worldwide ranked by ideXlab platform
Mario G Silveirinha - One of the best experts on this subject based on the ideXlab platform.
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design of linear to circular polarization transformers made of long densely packed metallic helices
IEEE Transactions on Antennas and Propagation, 2008Co-Authors: Mario G SilveirinhaAbstract:In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic Waves in a medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized Wave may be transformed into a circularly polarized Transmitted Wave, and that the transmission efficiency of such polarization transformer may be as high as 95%.
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design of linear to circular polarization transformers made of long densely packed metallic helices
arXiv: Materials Science, 2007Co-Authors: Mario G SilveirinhaAbstract:In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic Waves in medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized Wave may be transformed into a circularly polarized Transmitted Wave, and that the transmission efficiency of such polarization transformer may be as high as 95%. The theoretical results are supported by full Wave simulations.
Xiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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magnetic resonance hybridization and optical activity of microWaves in a chiral metamaterial
Applied Physics Letters, 2008Co-Authors: Hui Liu, S M Wang, Fuming Wang, Ping Chen, Shining Zhu, Xiang ZhangAbstract:The propagation of microWaves through a chiral metamaterial based on a magnetic dimer is experimentally studied. As proposed by our previous theoretical model, two resonance peaks are obtained in the transmission spectrum; these originate from the hybridization effect of magnetic resonance modes in this system. Optical activity is also observed in the transmission Wave. The polarization state dramatically changes around the resonance frequency: the Transmitted Wave becomes elliptically polarized with its major polarization axis approximately perpendicular to that of the linear incident Wave. This coupled magnetic dimer system provides a practical method to optically design tunable active medium and device.
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magnetic plasmon hybridization and optical activity at optical frequencies in metallic nanostructures
Physical Review B, 2007Co-Authors: Hui Liu, Shining Zhu, Dentcho A Genov, Yongmin Liu, Zhaowei Liu, Cheng Sun, Xiang ZhangAbstract:The excitation of optical magnetic plasmons in chiral metallic nanostructures based on a magnetic dimer is studied theoretically. Hybridization of the magnetic plasmon modes and a type of optical activity is demonstrated at near-infrared frequencies. A linearly polarized electromagnetic Wave is shown to change its polarization after passing through an array of magnetic dimers. The polarization of the Transmitted Wave rotates counterclockwise at incident light frequencies corresponding to the low energy and clockwise at the high energy magnetic plasmon state. A metamaterial made of a large number of coupled magnetic dimers could be utilized as a tunable optically active medium with possible applications in optical elements and devices.
Claude Depollier - One of the best experts on this subject based on the ideXlab platform.
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transient acoustic Wave propagation in air saturated porous media at low frequencies
Journal of Applied Physics, 2007Co-Authors: Zine El Abiddine Fellah, Mohamed Fellah, F G Mitri, Naima Sebaa, Walter Lauriks, Claude DepollierAbstract:This paper provides a temporal model of the direct scattering problem for the propagation of transient low frequency Waves in a homogeneous isotropic slab of porous material having a rigid frame. In this model, the inertial effects are described by the low frequency approximation of the tortuosity. The viscous and thermal losses of the medium are modeled by viscous and thermal permeabilities. The propagation equation is derived and solved analytically in the time domain. An original expression of Green’s function of the porous medium is obtained. The transmission scattering operator of the first Transmitted Wave is calculated and compared with experimental data.
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acoustic Wave propagation in a macroscopically inhomogeneous porous medium saturated by a fluid
Applied Physics Letters, 2007Co-Authors: L De Ryck, Zine El Abiddine Fellah, Walter Lauriks, Jeanphilippe Groby, Philippe Leclaire, Armand Wirgin, Claude DepollierAbstract:The equations of motion in a macroscopically inhomogeneous porous medium saturated by a fluid are derived. As a first verification of the validity of these equations, a two-layer rigid frame porous system considered as one single porous layer with a sudden change in physical properties is studied. A simple Wave equation is derived and solved for this system. The reflection and transmission coefficients are calculated numerically using a Wave splitting-Green's function approach (WS-GF). The reflected and Transmitted Wave time histories are also simulated. Experimental results obtained for materials saturated by air are compared to the results given by this approach and to those of the classical transfer matrix method (TMM).
L Yin - One of the best experts on this subject based on the ideXlab platform.
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surface plasmons at single nanoholes in au films
Applied Physics Letters, 2004Co-Authors: L Yin, Vitalii Vlaskovlasov, Andreas Rydh, J Pearson, U Welp, Shihhui Chang, Stephen K Gray, George C SchatzAbstract:The generation of surface plasmon polaritons (SPPs) at isolated nanoholes in 100nm thick Au films is studied using near-field scanning optical microscopy. Finite-difference time-domain calculations, some explicitly including a model of the scanning tip, are used to interpret the results. We find the holes act as point-like sources of SPPs and demonstrate that the interference between the SPP and a directly Transmitted Wave allows determination of the Wavelength, phase, and decay length of the SPP. The near-field intensity patterns can be manipulated by varying the angle and polarization of the incident beam.
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surface plasmons at single nanoholes in au films
arXiv: Materials Science, 2004Co-Authors: L Yin, Vitalii Vlaskovlasov, Andreas Rydh, J Pearson, U Welp, Shihhui Chang, Stephen K Gray, George C SchatzAbstract:The generation of surface plasmon polaritons (SPP's) at isolated nanoholes in 100 nm thick Au films is studied using near-field scanning optical microscopy (NSOM). Finite-difference time-domain calculations, some explicitly including a model of the NSOM tip, are used to interpret the results. We find the holes act as point-like sources of SPP's and demonstrate that interference between SPP's and a directly Transmitted Wave allows for determination of the Wavelength, phase, and decay length of the SPP. The near-field intensity patterns can be manipulated by varying the angle and polarization of the incident beam.
Jun Mei - One of the best experts on this subject based on the ideXlab platform.
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controllable transmission and total reflection through an impedance matched acoustic metasurface
New Journal of Physics, 2014Co-Authors: Jun MeiAbstract:A general design paradigm for a novel type of acoustic metasurface is proposed by introducing periodically repeated supercells on a rigid thin plate, where each supercell contains multiple cut-through slits that are filled with materials possessing different refractive indices but the same impedance as that of the host medium. When the Wavelength of the incident Wave is smaller than the periodicity, the direction of the Transmitted Wave with nearly unity transmittance can be chosen by engineering the phase discontinuities along the transverse direction. When the Wavelength is larger than the periodicity, even though the metasurface is impedance matched to the host medium, most of the incident energy is reflected back and the remaining portion is converted into a surface-bound mode. We show that both the Transmitted Wave control and the high reflection with the surface mode excitation can be interpreted by a unified analytic model based on mode-coupling theory. Our general design principle not only supplies the functionalities of reflection-type acoustic metasurfaces, but also exhibits unprecedented flexibility and efficiency in various domains of Wave manipulation for possible applications in fields like refracting, collimating, focusing or absorbing Wave energy.
