1,721,359 research outputs found
Phononic crystals and acoustic metamaterials : applications to guiding and filtering phenomena and acoustic isolation
No full textCette thèse est consacrée à l’étude de certaines propriétés nouvelles des cristaux phononiques et des métamatériaux acoustiques. La plupart des simulations numériques a été réalisée à l’aide de la méthode F.D.T.D. Une partie préliminaire a porté sur l’existence de bandes interdites dans un cristal phononique 2D constitué de cylindres d’acier dans l’eau et notamment une application originale au démultiplexage. Dans ce travail, nous nous sommes plus particulièrement intéressés au cas d’un cristal phononique à résonances localisées présentant de multiples gaps basses fréquences, nettement en dessous du gap de Bragg. Le cristal étudié est constitué de cylindres concentriques de matériaux ayant des constantes élastiques très différentes, immergés dans une matrice fluide. Il présente plusieurs zéros de transmission basses fréquences dont on a étudié les comportements en fonction des paramètres physiques et géométriques. Nous avons montré comment élargir ces zéros de transmission pour obtenir des bandes de fréquences interdites. Nous avons calculé les paramètres effectifs autour d’une résonance et montré que la densité effective massique pouvait devenir négative sur une certaine gamme de fréquence. La dernière partie de ce travail est consacrée à l’étude d’une structure originale 3D, constituée de piliers déposés sur une plaque fine, qui permet d’obtenir l’ouverture d’un gap très basse fréquence par rapport au gap de Bragg. Nous avons étudié les conditions d’existence des bandes interdites ainsi que certaines propriétés de guidage et de filtrage. Enfin, nous avons étudié la transmission entre deux substrats par l’intermédiaire d’un réseau périodique de piliers. Nous avons mis en évidence une transmission exaltée, associée à une résonance de Fano.This thesis is devoted to the study of some new properties of phononic crystals and acoustics metamaterials. Most of simulations were carried out using F.D.T.D. method. A preliminary part was devoted to the study of the existence of gaps in a 2D phononic crystal made up of steel cylinders in water and in particular an original application to demultiplexing. In this work, we are more particularly interested by a phononic crystal with localized resonances displaying several low frequencies gaps well below the Bragg gap. The studied crystal consists of concentric cylinders having different elastic constants, immersed in a fluid matrix. It presents several zeros of transmission at low frequencies whose behaviors were studied as a function of the physical and geometrical parameters. We showed how to widen these zeros of transmission to obtain prohibited gaps. We calculated effective parameters around a resonance and showed the possibility of negative effective mass density. The last part of this work is devoted to the study of an original 3D structure, consisted of pillars deposited on a thin plate, which makes it possible to obtain the opening of a very low frequency gap compared to the Bragg gap. We studied the conditions of existence of the forbidden bands as well as guiding and filtering properties of this structure. Finally, we studied the transmission between two substrates across a periodic array of pillars. We highlighted an enhanced transmission, associated to a Fano resonance
Modeling of nano-plasmonic and photonic structures : applications to filtering phenomenon and to the conception of bioplasmonic nanosensors
No full textCe travail porte sur la modélisation et simulation avec la méthode des différences finies (FDTD) de structures plasmonique et photoniques à l’échelle submicronique. Dans une première partie, nous avons modélisé la propagation des ondes électromagnétiques à travers des nano-guides diélectriques (air ou SiO2), pris en sandwich entre deux plaques métalliques (de type Metal-Isolant-Metal). L’excitation des plasmons-polaritons aux interfaces permet le guidage d’ondes lumineuses à une échelle sub-longueur d’onde. Nous avons étudié les propriétés de guidage dans le domaine du visible et de l’infrarouge proche, notamment le couplage du guide avec des nano-résonateurs en vue d’explorer des fonctionnalités telles que le filtrage sélectif ou par réjection ainsi que des dispositifs de démultiplexage. Ces mêmes propriétés ont été étudiées dans une structure photonique submicronique constituée de guides d’ondes d’InP entouré d’air, couplé à un ensemble de cavités. Ces nano et microstructures constituent les briques de base pour la conception de nouveaux circuits intégrés tout-optique. Dans une seconde partie de la thèse, on s’est intéressé à la modélisation de l’interaction des ondes électromagnétiques avec des nanoparticules d’or déposées sur un substrat de SiO2, et recouvertes d’une couche d’un matériau diélectrique. Ce type de structures est prometteur pour réaliser des nano-capteurs bioplasmoniques en vue de caractériser des produits biologiques déposés en faible quantité sur la surface du diélectrique. Nous avons montré que la fréquence de la réponse plasmonique des particules présente une variation oscillatoire périodique en fonction l’épaisseur du diélectrique, avec une amplitude des oscillations qui peut atteindre quelques dizaines de nanomètres. Nous avons étudié ce phénomène en fonction des paramètres géométriques des nanoparticules d’or et de l’indice du diélectrique qui les recouvrent. L’objectif est de comprendre comment ces paramètres influencent la gamme de fréquence plasmonique ainsi que la sensibilité du détecteur. Ce travail théorique a été confronté aux résultats expérimentaux réalisés par l’équipe Bio-Interfaces de L’IRI (Institut de recherche interdisciplinaire, Lille 1).This work concerns the modeling and simulation by the finite difference method (FDTD) of plasmonic and photonic structures at the submicron scale. In the first part of the thesis we studied the propagation of electromagnetic-waves through two different dielectric nanoscale waveguides (made out of air and SiO2), sandwiched between two metallic plates (Metal-insulator-Metal). The excitation of surface plasmon-polariton at the interfaces of such waveguides enables light waveguiding at the subwavelength domain. We did study the waveguiding properties in the visible and near infrared ranges of frequency. Coupling of the main waveguide with a nano-resonatorwas investigated to achieve optical operations as filtering (in rejection and selection) and demultiplexing. These same optical functionalities were studied in a submicron photonic structure which is constituted by waveguides of InP surrounded by air, coupled to several cavities. Such nano and microstructures are essential for the design of new all-optical integrated circuits. The second part of the thesis concerns modeling of electromagnetic-waves interaction with metallic (gold) nanoparticles deposited on a glass substrate (SiO2) and covered with a dielectric layer. These structures are promising for the conception of plasmonic nanosensors, which would be used to characterize small amount of biological molecules deposited on the dielectric layer surface. We have shown that the frequency of the plasmonic resonance of metallic particles exhibits an oscillatory variation with the thickness of the layer, with an amplitude reaching tens of nanometers. One investigated this phenomenon according to geometrical parameters of the gold particles and the refractive index of the dielectric layer covering the particles. The aim of such study is to understand how the physical and geometrical parameters influence the frequency range of the plasmonic resonance of the particles and the sensitivity of the nanosensor. This theoretical work was confronted with experimental results realized by Bio-interfaces team of IRI (Interdisciplinary institute of research, University of Lille 1)
Robustness of conventional and topologically protected edge states in phononic crystal plates
Full text linkMany efforts have been devoted to studying the robustness of topologically protected edge states in acoustics;
however, the robustness of conventional edge states is rarely reported. In this work we theoretically study
interface acoustic states appearing in finite arrays of resonators on a thin plate with topologically protected
and conventional designs. Topologically protected interface states are first analyzed by employing the concept of
breaking inversion symmetry within the unit cell of a honeycomb lattice for cylindrical and spherical resonators;
we further demonstrate the robustness of the wave propagation along a zigzag path containing sharp corners
and defects. In parallel, a conventional interface state is also designed and compared to the same situations.
We found that the conventional interface state suffers backscattering in the zigzag path while it can show a
more confined wave transport in some cases. The presence of a defect along the propagation path scatters the
conventional interface wave and in particular can prohibit full propagation in the presence of a localized state
at the defect. Then, we show that the immunity of the topologically protected design needs the interface to be
surrounded by at least two hexagons of the phononic crystals on both sides, especially at the sharp corners in the
zigzag path, while the conventional design only needs one hexagon of bulk media with the advantage of compact
wave transport. Position and height disorders are further introduced to the interface pillars for both designs. It
is revealed that in both designs, the transmission decreases quasilinearly with position disorder while it exhibits
an abrupt drop with height disorder showing a transition threshold. With high disorder perturbation, waves can
hardly enter the interface for the topologically protected design, while waves are trapped at the interface for the
conventional design. A certain robustness against disorder is exhibited for conventional edge states. This work
provides insight into the interface states in micro- and nanoscale characterization and figures out the behaviors
for both topologically protected and conventional interface states
Gradient index phononic crystals and metamaterials
Full text linkPhononic crystals and acoustic metamaterials
are periodic structures whose effective properties can be
tailored at will to achieve extreme control on wave propagation. Their refractive index is obtained from the homogenization of the infinite periodic system, but it is possible
to locally change the properties of a finite crystal in such
a way that it results in an effective gradient of the refractive index. In such case the propagation of waves can be
accurately described by means of ray theory, and different refractive devices can be designed in the framework of
wave propagation in inhomogeneous media. In this paper
we review the different devices that have been studied for
the control of both bulk and guided acoustic waves based
on graded phononic crystals
Conception de matériaux acoustiques artificiels structurés : super-réseaux piézoélectriques, lentilles à gradient d'indice, plaque de cristaux phononiques à base de piliers
No full textLes cristaux phononiques et métamatériaux acoustiques sont des matériaux structurés artificiels qui fournissent un moyen prometteur pour manipuler les ondes acoustiques avec de nombreuses applications potentielles nouvelles. Après une introduction à l'état de l'art, le chapitre 2 propose des multicouches actives à base de structures piézoélectriques résonnantes. Leur transmission et leurs propriétés effectives peuvent être contrôlées activement en changeant les conditions électriques. Le chapitre 3 développe des méthodes d'homogénéisation pour une plaque de cristal phononique et montre pour la première fois la possibilité de contrôler simultanément la propagation de toutes les ondes fondamentales de Lamb. La méthode est appliquée à la conception de lentilles à gradient d'indice. Le chapitre 4 propose un nouveau type de cristal phononique en plaque à base de piliers creux qui met en évidence de nouveaux modes fortement localisés, tels que les modes de galerie, aussi bien dans le gap de Bragg que dans un gap à basse fréquence. Ces modes peuvent être activement accordés en remplissant les parties creuses des piliers avec un liquide dont on contrôle la hauteur ou la température. Le chapitre 5 propose une métasurface acoustique comportant un pilier unique ou une ligne de piliers déposés sur une plaque. Ces piliers ont des modes de résonance dipolaires et monopolaires qui sont très sensibles aux paramètres géométriques des piliers. Nous étudions en détail l'amplitude et la phase des ondes émises lorsqu'une onde incidente est diffusée par les piliers et montrons qu'elles peuvent être décrites comme des ondes émises par les piliers résonnants comme sources d'ondes acoustiques.Phononic crystals and acoustic metamaterials are artificial structured materials which provide a promising way to manipulate acoustic/elastic waves with many novel potential applications. After an introduction to the state of the art, the 2nd chapter designs actively controlled multilayers with piezoelectric resonant structures. The corresponding transmission and effective properties can be tuned by changing the electric boundary conditions of the piezoelectric materials. The 3rd chapter develops homogenization methods for phononic crystal plates and demonstrates for the first time the possibility of controlling simultaneously all the fundamental Lamb waves. The full control method developed here is applied to the design of various gradient index lenses that can exhibit several functionalities such as wave focusing or wave beaming. The 4th chapter designs a new type of phononic crystal/metamaterial plate with hollow pillars that exhibits several new localized modes, such as whispering-gallery modes, inside both Bragg and low frequency band gaps. These modes can be actively tuned by filling the hollow parts with a liquid for which the height or the temperature is controlled. The 5th chapter proposes acoustic metasurface consisting of a single pillar or one line of pillars deposited on a thin plate. Local resonances of dipolar and monopolar symmetries can be characterized which are very sensitive to the pillar’s geometric parameters. We study the amplitude and phase of the waves resulting from the scattering of an incident wave by the pillars and show that they can be described as dipolar or monopolar waves emitted by the pillar resonators as acoustic sources
Rigorous simulation of nonlinear optomechanical coupling in micro- and nano-structured resonant cavities
Full text linkA numerical method aimed to predict the optomechanical dynamics in micro- and nano-structured resonant cavities is introduced here. The rigorousness of it is ensured by exploiting the harmonic version of the transformation optics (TO) technique and by considering all the energy-transduction contributions of electrostriction, radiation pressure, photoelasticity and moving boundaries. Since our full-wave approach implements a multi-modal analysis and also considers material losses, from both a mechanical and an optical point of view, a considerable step further has been made in respect to the standard optomechanical perturbative theory. The efficiency and the versatility of the strategy are tested by analysing the optomechanical behaviour of a corrugated Si-based nanobeam and comparing numerical results to experimental ones from the literature
Topological States in Twisted Pillared Phononic Plates
Full text linkIn recent years, the advances in topological insulator in the fields of condensed matter have
been extended to classical wave systems such as acoustic and elastic waves. However, the
quantitative robustness study of topological states which is indispensable in practical realization
is rarely reported. In this work, we proposed topologically protected edge states with zigzag, bridge
and armchair interfaces in a new twisted phononic plate. The robustness of non-trivial band gap in
bulk structure is clearly presented versus twisted angles, revealing a threshold of 5 degrees which
is the key fundamental information for the robustness of topological edge states. We further
defined a localized displacement ratio as an efficient parameter to characterize edge states. Due to
the different orientation of the three interfaces, zigzag and bridge edge states show higher
quantitative robustness in their localized displacement ratio. A map of robustness as a function of
both frequency and twisted angle highlights the better performance of the topological zigzag edge
state. Robustness is evaluated for twisted angle and for all possible types of interfaces for the first
time, which benefits for the design and fabrication of solid functional devices with great potential
applications
[Invited] Localized phoxonic modes and application to sensor devices
No full textPhotonic crystals and their acoustic counterpart, the so-called phononic crystals are now well-known for their ability to guide, control, and manipulate the propagation of the optic and acoustic waves. These properties are mainly related to the possibility of band gaps in their band structure that allow the existence of localized modes and confined optic/acoustic waves. Moreover, during the past few years, there has been an increasing interest towards structures exhibiting simultaneous phononic and photonic band gaps, the so-called phoxonic crystals, thus allowing dual confinement of phonons and photons. From the point of view of sensing applications, several papers have already shown the capability of photonic crystals for detecting small variations in the refractive index of gases and liquids and have opened the way to a platform for a new class of sensors. In contrast, phononic crystals have only been recently proposed as a possible platform for the investigation of the acoustic velocity of a liquid filling the hollow parts of the structure. Thus, the potentiality of different geometries of phononic crystals for sensing applications still needs several further investigations. Moreover, some of the structures may be suitable for a dual measurement of both acoustic and optical velocities of the analyte. The objective of this presentation is to partly fill the lack of knowledge in these topics. To make a phononic/photonic sensor, one needs to design a structure in which the transmission coefficient displays well-defined features that are very sensitive to the acoustic/optic velocity of the infiltrating liquid. These features should be relatively isolated in frequency in order to allow the sensing of the probed parameter on a sufficiently broad range. In this paper, we investigate theoretically the transmission spectra in several geometries of phononic crystals and discuss the physical origin of the peaks and dips in the spectra and their usefulness for the sensing applications. The emphasis will first be put on the phononic behaviors and then possibly completed with the trends of the photonic transmissions. For the sake of simplicity, the solid parts of the structures are assumed to be made of silicon. We will show that several situations are suitable for independent determinations of the acoustic velocity and the index of refraction of the liquid while some constraints can appear on the geometrical parameters to make a dual phononic/photonic sensor. The calculations are performed by using either a home-made Finite Difference Time Domain (FDTD) method or the Comsol Multiphysics Finite Element Method (FEM)
Acoustic waves focusing with elliptic pillars type metasurface
No full textInternational audienceWe numerically investigate the focusing properties of an acoustic metasurface consisting of a line ofpillars of elliptic shape on a thin plate. We report on the influence of the ellipticity parameter on both monopolarcompressional and dipolar bending modes of the pillars. We show that a line of pillars with a gradient in theirellipticity allows to focus the transmitted elastic wave at different targeted points
Low-power phonon lasing through position-modulated Kerr-type nonlinearity
No full textInternational audienceWe demonstrate low-power amplification process in cavity optomechanics (COM). This operation is based on the nonlinear position-modulated self-Kerr interaction. Owing to this nonlinear term, the effective coupling highly scales with the photon number, resulting in a giant enhancement of the cooperativity. Even for small nonlinearity, the system reaches the amplification threshold for weak driving strength, leading to low-power phonon lasing. This amplifier can be phase-preserving and provides a practical advantage related to the power consumption issues. This work opens up new avenues to perform low-power and efficient amplifiers in optomechanics and related fields
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