129 research outputs found
Invisibility and Inverse Problems
This survey of recent developments in cloaking and transformation optics is
an expanded version of the lecture by Gunther Uhlmann at the 2008 Annual
Meeting of the American Mathematical Society.Comment: 68 pages, 12 figures. To appear in the Bulletin of the AM
Realizability of metamaterials with prescribed electric permittivity and magnetic permeability tensors
We show that any pair of real symmetric tensors \BGve and \BGm can be
realized as the effective electric permittivity and effective magnetic
permeability of a metamaterial at a given fixed frequency. The construction
starts with two extremely low loss metamaterials, with arbitrarily small
microstructure, whose existence is ensured by the work of Bouchitt{\'e} and
Bourel and Bouchitt\'e and Schweizer, one having at the given frequency a
permittivity tensor with exactly one negative eigenvalue, and a positive
permeability tensor, and the other having a positive permittivity tensor, and a
permeability tensor having exactly one negative eigenvalue. To achieve the
desired effective properties these materials are laminated together in a
hierarchical multiple rank laminate structure, with widely separated length
scales, and varying directions of lamination, but with the largest length scale
still much shorter than the wavelengths and attenuation lengths in the
macroscopic effective medium.Comment: 12 pages, no figure
Invisible waveguides on metal plates for plasmonic analogues of electromagnetic wormholes
We introduce two types of toroidal metamaterials which are invisible to
surface plasmon polaritons (SPPs) propagating on a metal surface. The former is
a toroidal handlebody bridging remote holes on the metal surface: It works as a
kind of plasmonic counterpart of electromagnetic wormholes. The latter is a
toroidal ring lying on the metal surface: This bridges two disconnected metal
surfaces i.e. It connects a thin metal cylinder to a flat metal surface with a
hole. Full-wave numerical simulations demonstrate that an electromagnetic field
propagating inside these metamaterials does not disturb the propagation of SPPs
at the metal surface. A multilayered design of these devices is proposed, based
on effective medium theory for a set of reduced parameters: The former
plasmonic analogue of electromagnetic wormhole requires homogeneous isotropic
magnetic layers, while the latter merely requires dielectric layers.Comment: 17 figure
Electromagnetic wormholes via handlebody constructions
Cloaking devices are prescriptions of electrostatic, optical or
electromagnetic parameter fields (conductivity , index of refraction
, or electric permittivity and magnetic permeability
) which are piecewise smooth on and singular on a
hypersurface , and such that objects in the region enclosed by
are not detectable to external observation by waves. Here, we give related
constructions of invisible tunnels, which allow electromagnetic waves to pass
between possibly distant points, but with only the ends of the tunnels visible
to electromagnetic imaging. Effectively, these change the topology of space
with respect to solutions of Maxwell's equations, corresponding to attaching a
handlebody to . The resulting devices thus function as
electromagnetic wormholes.Comment: 25 pages, 6 figures (some color
Transformation bending device emulated by graded-index waveguide
We demonstrate that a transformation device can be emulated using a
gradient-index waveguide. The effective index of the waveguide is spatially
varied by tailoring a gradient thickness dielectric waveguide. Based on this
technology, we demonstrate a transformation device guiding visible light around
a sharp corner, with low scattering loss and reflection loss. The experimental
results are in good agreement with the numerical results.Comment: This paper is published at Optics Express 20, 13006 (2012
Effectiveness and improvement of cylindrical cloaking with the SHS lining
We analyze, both analytically and numerically, the effectiveness of cloaking
an infinite cylinder from observations by electromagnetic waves in three
dimensions. We show that, as truncated approximations of the ideal permittivity
and permeability tensors tend towards the singular ideal cloaking fields, so
that the anisotropy ratio tends to infinity, the and fields blow up
near the cloaking surface. We also consider cloaking with and without the SHS
(soft-and-hard surface) lining. We demonstrate numerically that cloaking is
significantly improved by the SHS lining, with both the far field of the
scattered wave significantly reduced and the blow up of and prevented.Comment: 22 pages, 2 color figure
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