65 research outputs found
A Onelab model for the parametric study of mono-dimensional diffraction gratings
This document aims at presenting both theoretical and practical aspects of
the grating_2D Onelab model (available at
http://onelab.info/wiki/Diffraction_grating). This model applies to so-called
mono-dimensional grating, i.e. structures having one direction of invariance.
Various geometries and materials can be handled or easily added. The two
classical polarization cases, denoted here E// and H//, are addressed. The
output consists in a full energy balance of the problem computed from the field
maps. This model is based on free the GNU softwares Gmsh, GetDP and their
interface Onelab.Comment: arXiv admin note: text overlap with arXiv:1302.103
Homogenization of 3D finite chiral photonic crystals
International audienceWe homogenize Maxwell's equations for Drude-Born-Fedorov chiral crystals, using the multi-scale technique. We find that the homogenized material is described by dispersive anisotropic effective matrices, derived from frequency-dependent coupled auxiliary problems. For low frequencies, these matrices may not be positive definite
Photonics in highly dispersive media: The exact modal expansion
We present exact modal expansions for photonic systems including highly
dispersive media. The formulas, based on a simple version of the Keldysh
theorem, are very general since both permeability and permittivity can be
dispersive, anisotropic, and even possibly non reciprocal. A simple dispersive
test case where both plasmonic and geometrical resonances strongly interact
exemplifies the numerical efficiency of our approach
Transmission enhancement through square coaxial apertures arrays in metallic film: when leaky modes filter infrared light
We consider arrays of square coaxial apertures in a gold layer and study
their diffractive behavior in the far infrared region. These structures exhibit
a resonant transmission enhancement that is used to design tunable bandpass
filters. We provide a study of their spectral features and show by a modal
analysis that the resonance peak is due to the excitation of leaky modes of the
open photonic structure. Fourier transform infrared (FTIR) spectrophotometry
transmission measurements of samples deposited on Si substrate show good
agreement with numerical results and demonstrate angular tolerance up to 30
degrees of the fabricated filters.Comment: 4 pages, 3 figure
Finite Element Method
International audienceIn this chapter, we demonstrate a general formulation of the Finite Element Method allowing to calculate the diffraction efficiencies from the electromagnetic field diffracted by arbitrarily shaped gratings embedded in a multilayered stack lightened by a plane wave of arbitrary incidence and polarization angle. It relies on a rigorous treatment of the plane wave sources problem through an equivalent radiation problem with localized sources. Bloch conditions and a new Adaptative Perfectly Matched Layer have been implemented in order to truncate the computational domain. We derive this formulation for both mono-dimensional gratings in TE/TM polarization cases (2D or scalar case) and for the most general bidimensional or crossed gratings (3D or vector case). The main advantage of this formulation is its complete generality with respect to the studied geometries and the material properties. Its principle remains independent of both the number of diffractive elements by period and number of stack layers. The flexibility of our approach makes it a handy and powerful tool for the study of metamaterials, finite size photonic crystals, periodic plasmonic structures..
Revolution analysis of three-dimensional arbitrary cloaks
We extend the design of radially symmetric three-dimensional invisibility
cloaks through transformation optics to cloaks with a surface of revolution. We
derive the expression of the transformation matrix and show that one of its
eigenvalues vanishes on the inner boundary of the cloaks, while the other two
remain strictly positive and bounded. The validity of our approach is confirmed
by finite edge-elements computations for a non-convex cloak of varying
thickness.Comment: 6 pages, 4 figure
Resonant metamaterial absorbers for infrared spectral filtering: quasimodal analysis, design, fabrication and characterization
We present a modal analysis of metal-insulator-metal (MIM) based
metamaterials in the far infrared region. These structures can be used as
resonant reflection bandcut spectral filters that are independent of the
polarization and direction of incidence because of the excitation of quasimodes
(modes associated with a complex frequency) leading to quasi-total absorption.
We fabricated large area samples made of chromium nanorod gratings on top of
Si/Cr layers deposited on silicon substrate and measurements by Fourier
Transform spectrophotometry show good agreement with finite element
simulations. A quasimodal expansion method is developed to obtain a reduced
order model that fits very well full wave simulations and that highlights
excitation conditions of the modes.Comment: 8 pages, 7 figure
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