646 research outputs found
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
Acoustic cloaking and mirages with flying carpets
Carpets under consideration here, in the context of pressure acoustic waves
propagating in a compressible fluid, do not touch the ground: they levitate in
mid-air (or float in mid-water), which leads to approximate cloaking for an
object hidden underneath, or touching either sides of a square cylinder on, or
over, the ground. The tentlike carpets attached to the sides of a square
cylinder illustrate how the notion of a carpet on a wall naturally generalizes
to sides of other small compact objects. We then extend the concept of flying
carpets to circular cylinders. However, instead of reducing its scattering
cross-section like in acoustic cloaks, we rather mimic that of another
obstacle, say a square rigid cylinder. For instance, show that one can hide any
type of defects under such circular carpets, and yet they still scatter waves
just like a smaller cylinder on its own. Interestingly, all these carpets are
described by non-singular acoustic parameters. To exemplify this important
aspect, we propose a multi-layered carpet consisting of isotropic homogeneous
fluids with constant bulk modulus and varying density which works over a finite
range of wavelengths. We have discussed some applications, with the sonar boats
or radars cases as typical examples. For instance, we would like to render a
pipeline lying on the bottom of the sea or floating in mid-water undetectable
for a boat with a sonar at rest just above it on the surface of the sea.
Another possible application would be protecting parabolic antennas.Comment: 26 pages, 9 figures. Key words: Mathematical methods in physics;
Mathematical Physics, electromagnetic theory; Metamaterials;Anisotropic
optical materials; invisibility; cloa
Combined Fictitious Sources - Scattering Matrix method
Combined Fictitious Sources - Scattering Matrix metho
Polarizability Expressions for Predicting Resonances in Plasmonic and Mie Scatterers
Polarizability expressions are commonly used in optics and photonics to model
the light scattering by small particles. Models based on Taylor series of the
scattering coefficients of the particles fail to predict the morphologic
resonances hosted by dielectric particles. Here, we propose to use the
factorization of the special functions appearing in the expression of the Mie
scattering coefficients to derive point-like models. These models can be
applied to reproduce both Mie resonances of dielectric particles and plasmonic
resonances of metallic particles. They provide simple but robust tools to
predict accurately the electric and magnetic Mie resonances in dielectric
particles.Comment: 11 pages, 7 figure
Seismic waves damping with arrays of inertial resonators
We investigate the elastic stop band properties of a theoretical cubic array
of iron spheres connected to a bulk of concrete via iron or rubber ligaments.
Each sphere can move freely within a surrounding air cavity, but ligaments
couple it to the bulk and further facilitate bending and rotational motions.
Associated low frequency local resonances are well predicted by an asymptotic
formula. We find complete stop bands (for all wave-polarizations) in the
frequency range Hertz (resp. Hertz) for -meter (resp.
-meter) diameter iron spheres with a -meter (resp. -meter)
center-to-center spacing, when they are connected to concrete via steel (resp.
rubber) ligaments. The scattering problem shows that only bending modes are
responsible for damping and that rotational modes are totally overwritten by
bending modes. Regarding seismic applications, we further consider soil as a
bulk medium, in which case the relative bandwidth of the low frequency stop
band can be enlarged through ligaments of different sizes that allow for well
separated bending and rotational modes. We finally achieve some damping of
elastodynamic waves from to Hertz (relative stop band of
percent) for iron spheres -meter in diameter that are connected to soil
with six rubber ligaments of optimized shapes. These results represent a
preliminary step in the design of seismic shields placed around, or underneath,
the foundations of large civil infrastructures
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