72 research outputs found
Light wheel buildup using a backward surface mode
3 pagesInternational audienceWhen a guided mode is excited in a dielectric slab coupled to a backward surface wave at the interface between a dielectric and a left-handed medium, light is confined in the structure : this is a light wheel. Complex plane analysis of the dispersion relation and coupled-mode formalism give a deep insight into the physics of this phenomenon (lateral confinement and the presence of a dark zone)
Analysis of Defect in Extreme UV Lithography Mask Using a Modal Method Based on Nodal B-Spline Expansion
This paper details to an electromagnetic modeling of an extreme ultraviolet (EUV) lithography mask. For that purpose, a modal method based on a spline nodal expansion (MMSNE) is presented. The results obtained using first, and second-order splines as basis functions are compared with those obtained using other modal methods, such as modal method by Fourier expansion (MMFE). The agreement between the results obtained using different methods is very good, and a convergence test is also performed. The spline nodal basis function implemented in this paper is the first step toward the realization of a multiresolution scheme that is expected to perform much more efficiently than conventional schemes
Modal expansion for the 2D Green's function in a non-orthogonal coordinates system.
We present an efficient modal method to calculate the two-dimensional Green's function for electromagnetics in curvilinear coordinates. For this purpose the coordinate transformation based differential method, introduced for the numerical analysis of surface-relief gratings, is directly used with perfectly matched layers (PMLs). The covariant formalism Maxwell's equations, very convenient for the non-orthogonal coordinates formulation, also gives an unified analysis of PMLs. Numerical results for a line source placed above a perfectly conducting corrugated surface are presented
Localization of light in a lamellar structure with left-handed medium : the light wheel
International audienceThe contra-directional coupling between a left-handed monomode waveguide and a right-handed monomode waveguide is rigorously studied using a complex plane analysis. Light is shown to rotate in this lamellar structure forming a very exotic mode which we have called a light wheel. The light wheel can be excited using evanescent coupling or by placing sources in one of the waveguides. This structure can thus be seen as a new type of cavity. It is a way to suppress the guided mode of a dielectric slab
MODAL METHOD BASED ON SUBSECTIONAL GEGEN- BAUER POLYNOMIAL EXPANSION FOR LAMELLAR GRATINGS: WEIGHTING FUNCTION, CONVERGENCE AND STABILITY
International audienceThe Modal Method by Gegenbauer polynomials Expan- sion (MMGE) has been recently introduced for lamellar gratings by Edee [8]. This method shows a promising potential of outstanding convergence but still suffers from instabilities when the number of polynomials is increased. In this work, we identify the origin of these instabilities and propose a way to remove them
Simple and accurate analytical model of planar grids and high-impedance surfaces comprising metal strips or patches
This paper introduces simple analytical formulas for the grid impedance of
electrically dense arrays of square patches and for the surface impedance of
high-impedance surfaces based on the dense arrays of metal strips or square
patches over ground planes. Emphasis is on the oblique-incidence excitation.
The approach is based on the known analytical models for strip grids combined
with the approximate Babinet principle for planar grids located at a dielectric
interface. Analytical expressions for the surface impedance and reflection
coefficient resulting from our analysis are thoroughly verified by full-wave
simulations and compared with available data in open literature for particular
cases. The results can be used in the design of various antennas and microwave
or millimeter wave devices which use artificial impedance surfaces and
artificial magnetic conductors (reflect-array antennas, tunable phase shifters,
etc.), as well as for the derivation of accurate higher-order impedance
boundary conditions for artificial (high-) impedance surfaces. As an example,
the propagation properties of surface waves along the high-impedance surfaces
are studied.Comment: 12 pages, 10 figures, submitted to IEEE Transactions on Antennas and
Propagatio
Light transmission by subwavelength square coaxial aperture arrays in metallic films
Using Fourier Modal Method, we study the enhanced transmission exhibited by arrays of square coaxial apertures in a metallic film. The calculated transmission spectrum is in good agreement with FDTD calculations. We show that the enhanced transmission can be explained considering a few guided modes of a coaxial waveguide
Atomic hydrogen in AGB circumstellar environments. A case study: X Her
We report the detection of the HI line at 21 cm from the circumstellar shell
around the AGB star X Her using the position-switching technique with the
Nancay Radio Telescope. At the star position the line shows 2 components: (i) a
broad one (FWHM ~ 13 km/s) centered at -72.2 km/s, and (ii) a narrow one (FWHM
\~ 4 km/s) centered at ~ -70.6 km/s. Our map shows that the source associated
to the broad component is asymmetric with material flowing preferentially
towards the North-East. This source extends to ~ 10 arcmin. (~ 0.4 pc) from the
star in that direction. On the other hand, the narrow component is detected
only at the star position and indicates material flowing away from the
observer. The total mass of atomic hydrogen is ~ 6.5 10^{-3} solar mass which,
within a factor 2, agrees with the estimate obtained from IRAS data at 60
microns.Comment: accepted for publication in MNRA
Gratings: Theory and Numeric Applications
International audienceThe book containes 11 chapters written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers
Gratings: Theory and Numeric Applications, Second Revisited Edition
International audienceThe second Edition of the Book contains 13 chapters, written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers.In comparison with the First Edition, we have added two more chapters (ch.12 and ch.13), and revised four other chapters (ch.6, ch.7, ch.10, and ch.11
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