84 research outputs found
Slow-wave effect and mode-profile matching in Photonic Crystal microcavities
Physical mechanisms involved in the light confinement in photonic crystal
slab microcavities are investigated. We first present a full three-dimensional
numerical study of these microcavities. Then, to gain physical insight into the
confinement mechanisms, we develop a Fabry-Perot model. This model provides
accurate predictions and sheds new light on the physics of light confinement.
We clearly identify two mechanisms to enhance the Q factor of these
microcavities. The first one consists in improving the mode-profile matching at
the cavity terminations and the second one in using a slow wave in the cavity.Comment: accepted for publication in Phys. Rev. B, 8 pages, 4 figure
A microscopic view of the electromagnetic properties of sub-wavelength metallic surfaces
We review the properties of the surface waves that are scattered by
two-dimensional sub-wavelength indentations on metallic surfaces. We show that
two distinct waves are involved, a surface plasmon polariton (SPP) and a
quasi-cylindrical wave (quasi-CW). We discuss the main characteristics of these
waves, their damping characteristic lengths and their relative excitation
weights as a function of the separation distance from the indentation and as a
function of the metal conductivity. In particular we show that derive a
closed-form expression for the quasi-CW, which clarifies its physical origin
and its main properties. We further present an intuitive microscopic model,
which explains how the elementary SPPs and quasi-CWs exchange their energies by
multiple-scattering to build up a rich variety of near- and far-field optical
effects.Comment: Review article, 98 references. Sur. Sc. Rep. (in press
Difference between penetration and damping lengths in photonic crystal mirrors
Different mirror geometries in two-dimensional photonic crystal slabs are
studied with fully-vectorial calculations. We compare their optical properties
and, in particular, we show that, for heterostructure mirrors, the penetration
length associated with the delay induced by distributed reflection is not
correlated to the characteristic damping length of the electromagnetic energy
distribution in the mirror. This unexpected result evidences that the usual
trade-off between short damping lengths and large penetration lengths that is
classically encountered in distributed Bragg reflectors can be overcome with
carefully designed photonic crystal structures.Comment: to be published in Applied Physics Letters, 4 pages, 4 figure
Optical extinction in a single layer of nanorods
We demonstrate that almost 100 % of incident photons can interact with a
monolayer of scatterers in a symmetrical environment. Nearly-perfect optical
extinction through free-standing transparent nanorod arrays has been measured.
The sharp spectral opacity window, in the form of a characteristic Fano
resonance, arises from the coherent multiple scattering in the array. In
addition, we show that nanorods made of absorbing material exhibit a 25-fold
absorption enhancement per unit volume compared to unstructured thin film.
These results open new perspectives for light management in high-Q, low volume
dielectric nanostructures, with potential applications in optical systems,
spectroscopy, and optomechanics
Tomographic imaging by coding and reconstruction
We present the various researches we made on tomographic imaging by coding and reconstruction . These works are based on
two chief kinds of methods : Coding Aperture Imaging and Transaxial Tomography, each of them including theoretical studies
and realization of tomographic systems for definite applications .
In this paper, we mainly present the more recent studies concerning reconstruction problems from missing data, with development
of an original method by "constrained natural pixels", and implementation of multislit coding in micro-imaging of laser plasmas .Nous présentons les divers travaux que nous avons réalisés sur l'imagerie tomographique par codage et reconstruction . Ces
travaux sont axés sur deux grands types de méthodes : l'Imagerie par Ouverture de Codage et la Tomographie Axiale
Transverse, et comprennent, pour chacune d'elles, des études théoriques et la conception de systèmes tomographiques pour
des applications bien précises .
Dans cet article, nous présentons essentiellement les études les plus récentes qui concernent les problèmes de reconstruction
à données incomplètes, avec le développement d'une méthode originale par «pixels naturels avec contrainte», et la mise en
ceuvre d'un codage par multifentes en micro-imagerie de plasmas laser
Surface plasmons of metallic surfaces perforated by nanoholes
Recent works dealt with the optical transmission on arrays of subwavelength
holes perforated in a thick metallic film. We have performed simulations which
quantitatively agree with experimental results and which unambiguously evidence
that the extraordinary transmission is due to the excitation of a
surface-plasmon-polariton (SPP) mode on the metallic film interfaces. We
identify this SPP mode and show that its near-field possesses a hybrid
character, gathering collective and localised effects which are both essential
for the transmission.Comment: 16 pages, 4 figure
Plasmonic Metasurface for Directional and Frequency-Selective Thermal Emission
International audienceIncandescent filaments and membranes are often used as infrared sources despite their low efficiency, broad angular emission, and lack of spectral selectivity. Here, we introduce a metasurface to control simultaneously the spectrum and the directivity of blackbody radiation. The plasmonic metasurface operates reliably at 600 °C with an emissivity higher than 0.85 in a narrow frequency band and in a narrow solid angle. This emitter paves the way for the development of compact, efficient, and cheap IR sources and gas detection systems
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