Les plasmons polaritons de surface (SPPs) jouent un rôle central en nanophotonique, parce que ce sont des modes optiques qui peuvent être confinés dans l’espace à l’échelle de 10 nm et dans le temps à l’échelle de 10 fs. L’excitation électrique des plasmons polaritons de surface par effet tunnel inélastique peut être ultrarapide et localisée, ce qui permet de développer une nanosource pour la nanophotonique intégrée en profitant pleinement du potentiel des polaritons plasmon de surface. Pourtant, ce processus est très inefficace avec un rendement de conversion typique de 10-7~10-5 plasmon par électron.Dans ce manuscrit de thèse, nous présentons une étude théorique et expérimentale qui vise à augmenter l’émission de plasmons de surface par effet tunnel inélastique avec une nano-antenne résonante. Nous avons développé un modèle théorique pour décrire l’émission de lumière à partir d’une jonction à effet tunnel en utilisant le théorème de fluctuation-dissipation. Nous proposons deux stratégies pour augmenter le rendement de conversion électron-plasmon. Nous introduisons un mode d’antenne résonnante confiné à l’échelle du nanomètre afin de renforcer le couplage entre le courant et le champ. En outre, nous introduisons l’hybridation d’un mode plasmonique metal/isolant/metal confiné et d’un mode d’antenne. Nous prédisons théoriquement que 30% de l’énergie émise par un dipôle est sous forme de SPP pour une longueur d’onde de travail de 800nm et une épaisseur d’isolant de 1 nm.Nous avons développé les processus de fabrication pour réaliser les antennes à effet tunnel en utilisant la configuration Al/AlOx/Au. L’antenne fabriquée présente une fonctionnalité robuste concernant les propriétés électriques et optiques. Nous montrons l’antenne permet de contrôler le spectre d’émission SPP, la polarisation d’émission SPP et renforcer l’efficacité des émissions de SPP de plus de 3 ordres de grandeur. La puissance totale émise sous forme de SPP est de l’ordre de 10 pW, quatre ordres de grandeur de plus que la puissance typique émise par une pointe de microscope à effet tunnel. / Surface plasmon polaritons (SPPs) plays a central role in nanophotonics because they are optical modes that can be confined in space at the 10 nm scale and in time at the 10 fs scale. Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons has the potential to be fast and localized so that it offers the opportunity to develop a nanosource for on-chip nanophotonics taking advantage of the full potential of surface plasmons polaritons. However, inelastic tunneling is rather inefficient with a typical electron-to-plasmon conversion efficiency of 10-7~10-5. In this thesis manuscript, we present a study for enhancing surface plasmon emission by inelastic tunneling electrons with a resonant nanoantenna. It consists of theoretical and experimental investigations. First, we have developed a theoretical model to describe the light emission from a tunnel junction based on the fluctuation-dissipation theorem. Second, we have theoretically demonstrated two strategies to improve the antenna SPP efficiency thus aiming to enhance electron-to-plasmon conversion efficiency. We introduce a resonant antenna mode with a sub-nanometer gap in order to enhance the coupling between the inelastic current and the the mode. Furthermore, we introduce the hybridization in a nanopatch antenna between a gap mode and an antenna mode to launch SPPs: we theoretically predict that 30% of the power emitted by a dipole is converted into SPP (working wavelength at 800nm) with a 1nm gap thickness. Third, we have developed the fabrication procedures to realize antenna tunnel junctions based on the Al/AlOx/Au configuration. The fabricated antenna junction shows a robust functionality both regarding electrical and optical properties. The antenna junction is demonstrated to control the SPP emission spectrum, the SPP emission polarization and enhance the SPP emission efficiency by over 3 orders of magnitude. The total SPP power emitted is in the range of 10 pW, four orders of magnitude larger than the typical fW power emitted by a scanning tunneling tip junction.

Electromagnetic processes induced by electron scattering off few-nucleon systems are theoretically investigated in the non-relativistic formalism. Non-relativistic one-body nuclear current operators are used with a parametrization of nucleon electromagnetic form factors based on recent experimental nucleon scattering data. Electromagnetic form factors of three-nucleon and four-nucleon systems are calculated from elastic electron-nucleus scattering information. Nuclear response functions used in the determination of differential cross sections for inclusive and exclusive quasi-elastic electron-nucleon scattering from the 4He nucleus are also calculated. Final-state interactions in the quasi-elastic nucleon knockout process are explicitly taken into account using the Glauber approximation. The sensitivity of the response functions to the final-state interactions is investigated. The Antisymmetrized Molecular Dynamics approach with angular momentum and parity projection is employed to construct ground state wave functions for the nuclei. A reduced form of the realistic Argonne V18 nucleon-nucleon potential is used to describe nuclear Hamiltonian. A convenient numerical technique of approximating expectation values of nuclear Hamiltonian operators is employed. The constructed wave functions are used to calculate ground-state energies, root-mean-square radii and magnetic dipole moments of selected light nuclei. The theoretical predictions of the nuclear properties for the selected nuclei give a satisfactory description of experimental values. The Glauber approximation is combined with the Antisymmetrized Molecular Dynamics to generate wave functions for scattering states in quasi-elastic scattering processes. The wave functions are then used to study proton knockout reactions in the 4He nucleus. The theoretical predictions of the model reproduce experimental observation quite well. / Physics / Ph D. (Physics)

Όταν ηλεκρομαγνητική (ΗΜ) ακτινοβολία, προερχόμενη από κάποια πηγή, προσπίπτει σε σύνολο από σωμάτια τότε λαμβάνουν χώρα δύο φαινόμενα. Πρώτον, ασκούνται δυνάμεις στα σωμάτια οι οποίες οφείλονται αποκλειστικά στην σκέδαση της ΗΜ ακτινοβολίας της πηγής από αυτά. Οι δυνάμεις αυτές ονομάζονται Optical Trapping Forces. Δεύτερον, τα ίδια τα σωμάτια σκεδάζοντας την ΗΜ ακτινοβολία της πηγής, λειτουργούν και αυτά ως πηγές ακτινοβολίας. Έτσι ασκούν δυνάμεις το ένα στο άλλο. Οι δυνάμεις αυτές ονομάζονται Optical Binding Forces. H παράλληλη δράση των δύο αυτών ειδών δυνάμεων έχει ως αποτέλεσμα την δημιουργία ευσταθών δομών από τα σωμάτια. Προκειμένου την θεωρητική πρόβλεψη των δομών που αναπτύσσονται, χρειαζόμαστε έναν ταχύτατο αλγόριθμο υπολογισμού των δυνάμεων. Ο πιο ταχύς αλγόριθμος θα είναι το αποτέλεσμα της εύρεσης ενός αναλυτικού τύπου υπολογισμού των δυνάμεων. Η κατασκευή και η παρουσίαση του αναλυτικού τύπου αυτού είναι και το περιεχόμενο της εργασίας που ακολουθεί. / When the electromagnetic radiation, originating from a source, meets an ensemble of particles, there are two phenomena which take place. First, there are forces acting on these particles due exclusively to the scattering of the electromagnetic radiation from the particles. These are the so-called “Optical Trapping Forces”. Second, particles themselves act as sources of radiation since they scatter the radiation, and they exert forces one to another. These are the so-called “Optical Binding Forces”. The coexistence of these two different forces results in the creation of stable structures where the particles are self-organized. To achieve the theoretical prediction of these structures, we need a very efficient algorithm to calculate the forces. The fastest possible and thus more efficient algorithm originates from the analytical formula of the forces. The construction and the solution of the forces analytical formula is the content of this research work.

Electromagnetic processes induced by electron scattering off few-nucleon systems are theoretically investigated in the non-relativistic formalism. Non-relativistic one-body nuclear current operators are used with a parametrization of nucleon electromagnetic form factors based on recent experimental nucleon scattering data. Electromagnetic form factors of three-nucleon and four-nucleon systems are calculated from elastic electron-nucleus scattering information. Nuclear response functions used in the determination of differential cross sections for inclusive and exclusive quasi-elastic electron-nucleon scattering from the 4He nucleus are also calculated. Final-state interactions in the quasi-elastic nucleon knockout process are explicitly taken into account using the Glauber approximation. The sensitivity of the response functions to the final-state interactions is investigated. The Antisymmetrized Molecular Dynamics approach with angular momentum and parity projection is employed to construct ground state wave functions for the nuclei. A reduced form of the realistic Argonne V18 nucleon-nucleon potential is used to describe nuclear Hamiltonian. A convenient numerical technique of approximating expectation values of nuclear Hamiltonian operators is employed. The constructed wave functions are used to calculate ground-state energies, root-mean-square radii and magnetic dipole moments of selected light nuclei. The theoretical predictions of the nuclear properties for the selected nuclei give a satisfactory description of experimental values. The Glauber approximation is combined with the Antisymmetrized Molecular Dynamics to generate wave functions for scattering states in quasi-elastic scattering processes. The wave functions are then used to study proton knockout reactions in the 4He nucleus. The theoretical predictions of the model reproduce experimental observation quite well. / Physics / Ph D. (Physics)

Les vapeurs atomiques confinées dans des cellules nanométriques constituent une plateforme intéressante pour la réalisation de senseurs atomiques. Dans cette thèse, nous étudions l’interaction entre la lumière et un ensemble d’atomes d’alcalins dans une telle cellule. Nous nous concentrons sur les phénomènes qui pourraient modifier la réponse optique du système et ainsi affecter la sensibilité du senseur. Premièrement, nous étudions la réponse non locale à la lumière induite par le mouvement des atomes dans la vapeur thermique. Quand la distance de relaxation des atomes excède la taille de la cellule, la réponse optique dépend de la taille du système. En transmission, nous avons montré que cela entraine une modification des propriétés de la vapeur avec une période égale à la longueur d’onde de la transition optique. Nous avons ensuite montré que lorsque la densité augmente, la réponse redevient locale. De plus, dans ce régime dense, l’interaction dipôle-dipôle résonnante engendre des déplacements de fréquences collectifs pour des ensembles sub-longueur d’onde. Nous avons démontré que ces shifts sont induits par la cavité formée par la cellule, clarifiant ainsi un débat de plus de 40 ans. Pour ce faire, nous avons développé un modèle pour extraire les effets de la densité déconvolués de ceux de la cavité. Proche des surfaces, la réponse optique des atomes est aussi impactée par l’interaction de van der Waals. Nous avons introduit une nouvelle méthode pour extraire avec précision la force de cette interaction. Nous avons également construit une nouvelle génération de nano-cellules super-polies en verre et enfin comparé les propriétés spectrales en transmission et spectroscopie hors d’axe. / Alkali vapors confined in nano-scale cells are promising tools for future integrated atom-based sensor. In this thesis, we investigate the interaction between light and an ensemble of atoms confined in a nano-geometry. We focus on the different processes that can modify the optical response of the atomic ensemble and possibly affect the sensitivity of a sensor based on that technology. First, we study the non-local response of atoms to a light excitation due the atomic motion in thermal vapors. When the distance over which the atoms relaxes is larger than the size of the cell, the optical response depends on the size of the system. We have observed that for transmission spectroscopy, this leads to a periodic modification of the optical response with a period equal to the wavelength of the optical transition. Subsequently we showed that when the density of atom increases, the atomic response becomes local again. In this dense regime, the resonant dipole-dipole interaction in a sub-wavelength geometry leads to collective frequency shifts of the spectral lines. We demonstrate that these shifts were induced by the cavity formed by the cell walls, hence clarifying a long-standing issue. We developed a model to extract the density shifts deconvolved from the cavity effects. Close to a surface, the optical response is also affected by the van der Waals atom-surface interaction. We introduced a new method to extract precisely the strength of this interaction. We also developed a new generation of super-polished glass nano-cells and we presented promising spectroscopic signals. Finally, using these cells, we have compared transmission and off-axis spectroscopic techniques.