Browsing by Author "Pendry, JB"

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    Cross-section comparisons of cloaks designed by transformation optical and optical conformal mapping approaches
    (Journal of Optics, 2011-02-01) Urzhumov, YA; Kundtz, NB; Smith, DR; Pendry, JB
    We review several approaches to optical invisibility designed using transformation optics (TO) and optical conformal mapping (CM) techniques. TO is a general framework for solving inverse scattering problems based on mimicking spatial coordinate transformations with distributions of material properties. There are two essential steps in the design of TO media: first, a coordinate transformation that achieves some desired functionality, resulting in a continuous spatial distribution of constitutive parameters that are generally anisotropic; and, second, the reduction of the derived continuous constitutive parameters to a metamaterial that serves as a stepwise approximation. We focus here on the first step, discussing the merits of various TO strategies proposed for the long-sought 'invisibility cloak'-a structure that renders opaque objects invisible. We also evaluate the cloaking capabilities of structures designed by the related CM approach, which makes use of conformal mapping to achieve index-only material distributions. The performance of the various cloaks is evaluated and compared using a universal measure-the total (all-angle) scattering cross section. © 2011 IOP Publishing Ltd.
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    Probing the ultimate limits of plasmonic enhancement.
    (Science, 2012-08-31) Ciracì, C; Hill, RT; Mock, JJ; Urzhumov, Y; Fernández-Domínguez, AI; Maier, SA; Pendry, JB; Chilkoti, A; Smith, DR
    Metals support surface plasmons at optical wavelengths and have the ability to localize light to subwavelength regions. The field enhancements that occur in these regions set the ultimate limitations on a wide range of nonlinear and quantum optical phenomena. We found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response. A semiclassical model of the electronic response of a metal places strict bounds on the ultimate field enhancement. To demonstrate the accuracy of this model, we studied optical scattering from gold nanoparticles spaced a few angstroms from a gold film. The bounds derived from the models and experiments impose limitations on all nanophotonic systems.