Compact metallo-dielectric optical antenna for ultra directional and enhanced radiative emission

We report the design of highly efficient optical antennas employing a judicious synthesis of metallic and dielectric materials. In the proposed scheme, a pair of metallic coupled nanoparticles permits large enhancements in both excitation strength and radiative decay rates, while a high refractive index dielectric microsphere is employed to efficiently collect light without spoiling the emitter quantum efficiency. Our simulations indicate potential fluorescence rate enhancements of 3 orders of magnitude over the entire optical frequency range

Recursive T matrix algorithm for resonant multiple scattering: Applications to localized plasmon excitations

A matrix balanced version of the Recursive Centered T Matrix Algorithm (RCTMA) applicable to systems possessing resonant inter-particle couplings is presented. Possible domains of application include systems containing interacting localized plasmon resonances, surface resonances, and photonic jet phenomena. This method is of particular interest when considering modifications to complex systems. The numerical accuracy of this technique is demonstrated in a study of particles with strongly interacting localized plasmon resonances

Mode-balancing far field control of light localization in nanoantennas

Light localization is controlled at a scale of lambda/10 in the harmonic regime from the far field domain in a plasmonic nanoantenna. The nanoantenna under study consists of 3 aligned spheres 50 nm in diameter separated by a distance of 5 nm. By simply tuning the orientation of an incident plane wave, symmetric and antisymmetric mode-balancing induces a strong enhancement of the near field intensity in one cavity while nullifying the light intensity in the other cavity. Furthermore, it is demonstrated that the dipolar moment of a plasmonic particle can be fully extinguished when strongly coupled with a dimer of identical nanoparticles. Consequently, optical transparency can be achieved in an ultra-compact symmetric metallic structure

Polarizability Expressions for Predicting Resonances in Plasmonic and Mie Scatterers

Polarizability expressions are commonly used in optics and photonics to model the light scattering by small particles. Models based on Taylor series of the scattering coefficients of the particles fail to predict the morphologic resonances hosted by dielectric particles. Here, we propose to use the factorization of the special functions appearing in the expression of the Mie scattering coefficients to derive point-like models. These models can be applied to reproduce both Mie resonances of dielectric particles and plasmonic resonances of metallic particles. They provide simple but robust tools to predict accurately the electric and magnetic Mie resonances in dielectric particles.Comment: 11 pages, 7 figure

Multipole methods for nanoantennas design: applications to Yagi-Uda configurations

International audienceWe present a detailed formalism allowing analytical calculations of the radiative properties of nanoantennas. This formalism does not rely on dipole approximations and utilizes multipolar multiple-scattering theory. The improvement in both accuracy and calculation speeds offered by this formulation provides significant advantages that are used in this work to study Yagi-Uda-type nanoantennas. We provide a study that questions the necessity of the reflector particle in nanoantennas

Three-dimensional subwavelength confinement of light with dielectric microspheres

International audienceDielectric microspheres are shown to be capable of confining light in a three-dimensional region of subwavelength dimensions when they are illuminated by tightly focused Gaussian beams. We show that a simple configuration, not involving resonances, permits one to reach an effective volume as small as 0.6 (l/n)3. It is shown that this three-dimensional confinement arises from interferences between the field scattered by the sphere and the high angular components of the incident Gaussian beam passing aside the sphere

Global polarizability matrix method for efficient modeling of light scattering by dense ensembles of non-spherical particles in stratified media

We introduce a numerical method that enables efficient modelling of light scattering by large, disordered ensembles of non-spherical particles incorporated in stratified media, including when the particles are in close vicinity to each other, to planar interfaces and/or to localized light sources. The method consists in finding a small set of fictitious polarizable elements -- or numerical dipoles -- that quantitatively reproduces the field scattered by an individual particle for any excitation and at an arbitrary distance from the particle surface. The set of numerical dipoles is described by a global polarizability matrix that is determined numerically by solving an inverse problem relying on fullwave simulations. The latter are classical and may be performed with any Maxwell's equations solver. Spatial non-locality is an important feature of the numerical dipoles set, providing additional degrees of freedom compared to classical coupled dipoles to reconstruct complex scattered fields. Once the polarizability matrix describing scattering by an individual particle is determined, the multiple scattering problem by ensembles of such particles in stratified media can be solved using a Green tensor formalism and only few numerical dipoles, thereby with a low physical memory usage, even for dense systems in close vicinity to interfaces. The performance of the method is studied with the example of large high-aspect-ratio high-index dielectric cylinders. The method is easy to implement and may offer new possibilities for the study of complex nanostructured surfaces, which are becoming widespread in emerging photonic technologies

Optimal interactions of light with magnetic and electric resonant particles

This work studies the limits of far and near-field electromagnetic response of sub-wavelength scatterers, like the unitary limit and of lossless scatterers, and the ideal absorption limit of lossy particles. These limit behaviors are described in terms of analytic formulas that approximate finite size effects while rigorously including radiative corrections. This analysis predicts the electric and/or magnetic limit responses of both metallic and dielectric nanoparticles while quantitatively describing near-field enhancements.Comment: 9 pages, 8 figures, 2 table

Microlentilles et nanoantennes optiques

Cette thèse étudie les interactions de la lumière avec des particules de taille mierométrique et nanométrique. Les particules sont des composants optiques s'inscrivant dans un besoin de miniaturisation des systèmes optiques. Deux grands types de particules sont distingués dans ce manuscrit. D'une part, les particules diélectriques de taille mierométriques permettent de focaliser la lumière de manière analogue aux lentilles conventionnelles. Nous avons démontre que lorsque cette même bille est éclairée par un faisceau préalablement focalisé, une interférence destructive permet de réduire significativement le volume focal dans toutes les directions de l'espace. Il est important de noter que de telles performances n'avaient été réalisées qu'à l'aide de structures complexes de type métalliques ou de cristaux photoniques. Un second type de particules connaissant un regain d'intérêt en optique sont les particules métalliques qui supportent des résonances plasmoniques dans le domaine optique. Ces résonances produisent d'intenses champs électromagnétiques au voisinage de particules nanométriques, plus petites que la longueur d'onde optique. De fortes interactions entre plasmons localisés permettent également un contrôle de la position du point focal à des échelles bien inférieures à la longueur d'onde optique incidente. Du fait des dimensions de l'ordre du nanomètre des volumes de focalisation de ces nanolentilles , il devient possible d'interagir directement avec un émetteur unique placé dans le voisinage de la particule comme une molécule fluorescente ou une boite quantique. La particule permet d'augmenter et de réorienter le signal émis par l'émetteur dans son voisinage. La particule joue ainsi le rôle de nanoantenne permettant de coupler une onde propagative à un état localisé de la matière et réciproquementAIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF