25-nm diamond crystals hosting single NV color centers sorted by photon-correlation near-field microscopy

Diamond nanocrystals containing highly photoluminescent color centers are attractive non-classical and near-field light sources. For near-field applications the size of the nanocrystal is crucial since it defines the optical resolution. NV (Nitrogen-Vacancy) color centers are efficiently created by proton irradiation and annealing of a nanodiamond powder. Using near-field microscopy and photon statistics measurements, we show that nanodiamond with size down to 25 nm can hold a single NV color center with bright and stable photoluminescence

Decision making based on optical excitation transfer via near-field interactions between quantum dots

Optical near-field interactions between nanostructured matter, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain

Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides

Single surface plasmon polaritons are excited using photons generated via spontaneous parametric down-conversion. The mean excitation rates, intensity correlations and Fock state populations are studied. The observed dependence of the second order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date (web): March 27 (2012

Développement et applications de sondes actives en microscopie en champ proche optique

In Near-eld Scanning Optical Microscopy (NSOM), a sub-wavelength source of light is driven in the vicinity of the sample studied, at small distances compared to lambda. Raster scanning the probe in front of the sample allows one to build an image with a resolution limited by the size of the source of light, not by diffraction. A single nanoparticle (size smaller than 10 nm) as source of light would allow one to reach genuinly nanometric resolutions.A dual confocal/NSOM microscope has been developped, in order to study and use such nanoparticles. Thanks to that microscope, images using the fluorescence of a single CdSe/ZnTe nanocrystal (~ 4 nm), attached to the apex of a standard NSOM tip, as source of light, have been acquired. The fluorescence blinking and photobleaching of those nanocrystals prevented us from building a complete image and therefore no discussion about the resolution reached is possible. We investigated other nanoparticles exhibiting no luminescence blinking or bleaching. The first candidate is YAG :Ce3+ agregates produced by LECBD, whose size is under 5 nm. The first optical caracterizations of those particles are presented. The second candidates are diamond nanoparticles doped by NV-centres. We show that our experimental set-up allows to select the luminescent particles, quantify their size and nd the ones that are doped with a single centre. Moreover it is possible to in-situ determine the charge of the center. Thus we demonstrate that our NSOM easily detects a single NV centre in a 25 nm diamond nanoparticle. This opens the possibility to use a particle of size as small as possible as source of light.En microscopie optique en champ proche (NSOM, Near-Field Scanning Optical Microscopy), une source de lumière de dimension très inférieure à la longueur d'onde est approchée de l'échantillon à étudier, à des distances très inférieures à lambda. En balayant la sonde en face de l'échantillon, on reconstruit une image optique d'une résolution non limitée par la diffraction, mais par la taille de la source de lumière utilisée. L'utilisation d'une nanoparticule (de taille de l'ordre de 10 nm) luminescente unique comme source de lumière permettrait donc d'avoir accès à des résolutions réellement nanométriques.Nous avons développé un microscope dual confocal/NSOM adapté à l'étude et l'utilisation de telles nanoparticules. A l'aide de ce microscope, nous avons acquis des images construites en utilisant la fluorescence d'un nanocristal de CdSe/ZnSe unique (~ 4 nm) rapporté en extrémité d'une pointe NSOM normale comme source de lumière. Le caractère intermittent de cette fluorescence, combiné avec le photoblanchiment de ces nanocristaux, ont empêché de reconstruire des images complètes permettant de quantifier la résolution latérale atteinte. Notre recherche s'est ensuite portée vers la caractérisation d'autres nanoparticules dont la luminescence ne présente ni blanchiment, ni clignotement. Le premier type de particules présentant ces caractéristiques sont des agrégats de YAG :Ce3+ produits par LECBD, d'une taille inférieure à 5 nm. Nous décrivons les premières caractérisations optiques de ces nanoparticules. La seconde alternative réside dans les nanoparticules de diamant dopées avec des centres NV. Nous avons démontré que notre dispositif permet de sélectionner les nano-diamants qui sont fluorescents, de mesurer leur taille et, dans le cas des particules fluorescentes, de déterminer celles qui hébergent un seul centre NV unique dont l'état de charge est de plus déterminé in situ. Nous montrons ainsi que notre NSOM détecte aisément le centre NV unique dans une nanoparticule de diamant de 25 nm. Cette démonstration ouvre la perspective de pouvoir utiliser une telle particule mais de taille arbitrairement petite comme source de lumière

Développement et applications de sondes actives en microscopie en champ proche optique

Une sonde active en microscopie en champ proche optique (NSOM) utilise la luminescence d'une nanoparticule unique comme source de lumière pour imager un échantillon. L'utilisation d'une telle sonde devrait permettre d'atteindre une résolution latérale optique limitée par la taille de la particule. La mise en oeuvre d'une sonde active se heurte à trois verrous importants: il faut maîtriser la technique de champ proche adaptée, disposer de particules présentant les bonnes caractéristiques d'émission et enfin parvenir à rapporter ces particules sur une sonde NSOM traditionnelle. Au cours de cette thèse, un microscope NSOM/confocal adapté à ces applications a été réalisé. Les résultats d'imagerie obtenus avec des sondes à base de nanocristaux de CdSe sont présentés. Des études prospectives d'autres particules pouvant être utilisées dans ce cadre sont aussi présentées: des oxydes de terres rares dopés, ainsi que des nanodiamants (diamètre inférieur à 25 nm) dopés par des centres colorés.ln near-field optical microcsopy (NSOM), an active tip uses a single nanoparticle's luminescence as source of light to image a sample. Such probe should allow one to reach a lateral optical resolution only limited by the size of the particle. Implementing an active tip faces three main issues: a suitable near-field environment, and particles displaying suitable emission characteristics have to be available, and eventually those particles have to be attached at the end of a standard NSOM tip. During this thesis, a NSOM/confocal microscope designed for such applications has been developped. Imaging experiments using a single CdSe nanocrystal have been presented. Prospective studies on other particles fit for such applications are presented : doped rare-earths oxides and nanodiamonds (diameter smaller than 25 nm) doped by col or center.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Self assembly drives quantum dot photoluminescence

International audienceEngineering the spectral properties of quantum dots can be achieved by a control of the quantum dots organization on a substrate. Indeed, many applications of quantum dots as LEDs are based on the realization of a 3D architecture of quantum dots. In this contribution, we present a systematic study of the quantum dot organization obtained on different chemically modified substrates. By varying the chemical affinity between the quantum dots and the substrate, the quantum dot organization is strongly modified from the 2D monolayer to the 3D aggregates. Then the photoluminescence of the different obtained samples has been systematically studied and correlated with the quantum dot film organization. We clearly show that the interaction between the substrate and the quantum dot must be stronger than the quantum dot–quantum dot interaction to avoid 3D aggregation and that these organization strongly modified the photoluminescence of the film rather than intrinsic changes of the quantum dot induced by pure surface chemistry