3,364 research outputs found
Near field interaction of microwave signals with a bounded plasma plume
The objective was to study the effect of the arcjet thruster plume on the performance of an onboard satellite reflector antenna. A project summary is presented along with sections on plasma and electromagnetic modeling. The plasma modeling section includes the following topics: wave propagation; plasma analysis; plume electron density model; and the proposed experimental program. The section on electromagnetic modeling includes new developments in ray modeling and the validation of three dimensional ray results
Lorenz-Mie theory for 2D scattering and resonance calculations
This PhD tutorial is concerned with a description of the two-dimensional
generalized Lorenz-Mie theory (2D-GLMT), a well-established numerical method
used to compute the interaction of light with arrays of cylindrical scatterers.
This theory is based on the method of separation of variables and the
application of an addition theorem for cylindrical functions. The purpose of
this tutorial is to assemble the practical tools necessary to implement the
2D-GLMT method for the computation of scattering by passive scatterers or of
resonances in optically active media. The first part contains a derivation of
the vector and scalar Helmholtz equations for 2D geometries, starting from
Maxwell's equations. Optically active media are included in 2D-GLMT using a
recent stationary formulation of the Maxwell-Bloch equations called
steady-state ab initio laser theory (SALT), which introduces new classes of
solutions useful for resonance computations. Following these preliminaries, a
detailed description of 2D-GLMT is presented. The emphasis is placed on the
derivation of beam-shape coefficients for scattering computations, as well as
the computation of resonant modes using a combination of 2D-GLMT and SALT. The
final section contains several numerical examples illustrating the full
potential of 2D-GLMT for scattering and resonance computations. These examples,
drawn from the literature, include the design of integrated polarization
filters and the computation of optical modes of photonic crystal cavities and
random lasers.Comment: This is an author-created, un-copyedited version of an article
published in Journal of Optics. IOP Publishing Ltd is not responsible for any
errors or omissions in this version of the manuscript or any version derived
from i
Electromagnetic Scattering by Cylinders - An Introduction
Investigating electromagnetic scattering by cylinders using Rayleigh-Gans theor
Scattering Suppression from Arbitrary Objects in Spatially-Dispersive Layered Metamaterials
Concealing objects by making them invisible to an external electromagnetic
probe is coined by the term cloaking. Cloaking devices, having numerous
potential applications, are still face challenges in realization, especially in
the visible spectral range. In particular, inherent losses and extreme
parameters of metamaterials required for the cloak implementation are the
limiting factors. Here, we numerically demonstrate nearly perfect suppression
of scattering from arbitrary shaped objects in spatially dispersive
metamaterial acting as an alignment-free concealing cover. We consider a
realization of a metamaterial as a metal-dielectric multilayer and demonstrate
suppression of scattering from an arbitrary object in forward and backward
directions with perfectly preserved wavefronts and less than 10% absolute
intensity change, despite spatial dispersion effects present in the composite
metamaterial. Beyond the usual scattering suppression applications, the
proposed configuration may serve as a simple realisation of scattering-free
detectors and sensors
Waveguiding power of photonic crystal slabs
We consider the waveguiding by thin patterned slabs embedded in a homogeneous
medium. In the longwave limit, the wave spectra of slabs are found to be well
described by a single frequency-independent parameter, which we call the
"guiding power". The guiding power can be evaluated in an effective medium
approximation, similar to the Maxwell Garnett theory, but modified for the
local field corrections specific to the two-dimensional geometry. The guiding
power is different for the transverse magnetic (TM) and transverse electric
(TE) polarizations. We show that the confinement factor of TM waves in a porous
layer with high index ratio can exceed that for a homogeneous layer. Similarly
enhanced confinement of TM waves is demonstrated for a layer of elongated
cylinders or elliptic inclusion with a high axis length ratio. The effect
originates from the suppression of local field effects and the increasing
internal field in the inclusion. It may be useful in the design of far-infrared
or THz quantum cascade lasers.Comment: 15 pages, 5 figure
Illusion Media: Generating Virtual Objects Using Realizable Metamaterials
We propose a class of optical transformation media, illusion media, which
render the enclosed object invisible and generate one or more virtual objects
as desired. We apply the proposed media to design a microwave device, which
transforms an actual object into two virtual objects. Such an illusion device
exhibits unusual electromagnetic behavior as verified by full-wave simulations.
Different from the published illusion devices which are composed of left-handed
materials with simultaneously negative permittivity and permeability, the
proposed illusion media have finite and positive permittivity and permeability.
Hence the designed device could be realizable using artificial metamaterials.Comment: 9 pages, 4 figures, published in Appl. Phys. Lett
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