3,528 research outputs found
Casimir effect across a layered medium
Using nonstandard recursion relations for Fresnel coefficients involving
successive stacks of layers, we extend the Lifshitz formula to configurations
with an inhomogeneous, n-layered, medium separating two planar objects. The
force on each object is the sum of a Lifshitz like force and a force arising
from the inhomogeneity of the medium. The theory correctly reproduces very
recently obtained results for the Casimir force/energy in some simple systems
of this kind. As a by product, we obtain a formula for the force on an
(unspecified) stack of layers between two planar objects which generalizes our
previous result for the force on a slab in a planar cavity.Comment: 5 pages, 1 figure, presented at QFEXT1
Dyadic Green's Functions and Guided Surface Waves for a Surface Conductivity Model of Graphene
An exact solution is obtained for the electromagnetic field due to an
electric current in the presence of a surface conductivity model of graphene.
The graphene is represented by an infinitesimally-thin, local and isotropic
two-sided conductivity surface. The field is obtained in terms of dyadic
Green's functions represented as Sommerfeld integrals. The solution of
plane-wave reflection and transmission is presented, and surface wave
propagation along graphene is studied via the poles of the Sommerfeld
integrals. For isolated graphene characterized by complex surface conductivity,
a proper transverse-electric (TE) surface wave exists if and only if the
imaginary part of conductivity is positive (associated with interband
conductivity), and a proper transverse-magnetic (TM) surface wave exists when
the imaginary part of conductivity is negative (associated with intraband
conductivity). By tuning the chemical potential at infrared frequencies, the
sign of the imaginary part of conductivity can be varied, allowing for some
control over surface wave properties.Comment: 9 figure
Recursion relations for generalized Fresnel coefficients: Casimir force in a planar cavity
We emphasize and demonstrate that, besides using the usual recursion
relations involving successive layers, generalized Fresnel coefficients of a
multilayer can equivalently be calculated using the recursion relations
involving stacks of layers, as introduced some time ago [M. S. Tomas, Phys.
Rev. A 51, 2545 (1995)]. Moreover, since the definition of the generalized
Fresnel coefficients employed does not imply properties of the stacks, these
nonstandard recursion relations can be used to calculate Fresnel coefficients
not only for local systems but also for a general multilayer consisting of
various types (local, nonlocal, inhomogeneous etc.) of layers. Their utility is
illustrated by deriving a few simple algorithms for calculating the
reflectivity of a Bragg mirror and extending the formula for the Casimir force
in a planar cavity to arbitrary media.Comment: 5 pages, 2 figures, slightly expande
Fast algorithm for scattering from planar arrays of conducting patches
Cataloged from PDF version of article.A direct (noniterative) algorithm for the solution
of the electromagnetic scattering from three-dimensional planar
arrays of conducting patches is developed. For an N-unknown
problem, the computational complexity of this new solution technique
is shown to be O(N2 log2N), which is considerably lower
than the O(N3) computational complexity of the conventional
direct solution techniques. The advantages of the reduction in
the computational complexity is pronounced in the solution of
large electromagnetics problems, such as scattering from large
and finite arrays of patches, synthesis and analysis of finite-sized
frequency selective surfaces (FSS’s), and radiation and scattering
from large phased-array antennas, to name a few
Efficiency of tunable band-gap structures for single-photon emission
The efficiency of recently proposed single-photon emitting sources based on
tunable planar band-gap structures is examined. The analysis is based on the
study of the total and ``radiative'' decay rates, the expectation value of
emitted radiation energy and its collimating cone. It is shown that the scheme
operating in the frequency range near the defect resonance of a defect band-gap
structure is more efficient than the one operating near the band edge of a
perfect band-gap structure.Comment: 9 pages, 7 figure
Casimir-Polder interaction between an atom and a dielectric slab
We present an explicit analytic calculation of the energy-level shift of an
atom in front of a non-dispersive and non-dissipative dielectric slab. We work
with the fully quantized electromagnetic field, taking retardation into
account. We give the shift as a two-dimensional integral and use asymptotic
analysis to find expressions for it in various retarded and non-retarded
limiting cases. The results can be used to estimate the energy shift of an atom
close to layered microstructures.Comment: 10 pages, incl 7 figure
The scattering of a cylindrical invisibility cloak: reduced parameters and optimization
We investigate the scattering of 2D cylindrical invisibility cloaks with
simplified constitutive parameters with the assistance of scattering
coefficients. We show that the scattering of the cloaks originates not only
from the boundary conditions but also from the spatial variation of the
component of permittivity/permeability. According to our formulation, we
propose some restrictions to the invisibility cloak in order to minimize its
scattering after the simplification has taken place. With our theoretical
analysis, it is possible to design a simplified cloak by using some peculiar
composites like photonic crystals (PCs) which mimic an effective refractive
index landscape rather than offering effective constitutives, meanwhile
canceling the scattering from the inner and outer boundaries.Comment: Accepted for J. Phys.
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