Leakage radiation microscopy of surface plasmons launched by a nanodiamond-based tip

Leakage-radiation microscopy of a thin gold film demonstrates the ability of an ensemble of fluorescent diamond nanoparticles attached onto the apex of an optical tip to serve as an efficient near-field surface-plasmon polariton launcher. The implementation of the nanodiamond-based tip in a near-field scanning optical microscope will allow for an accurate control on the launching position, thereby opening the way to scanning plasmonics.Comment: 21st European Conf. on Diamond, Diamond- Like Materials, Carbon Nanotubes, and Nitrides: "Diamond 2010", Budapest, September 2010 (Oral by OM

Directional silicon nano-antennas for quantum emitter control designed by evolutionary optimization

We optimize silicon nano-antennas to enhance and steer the emission of local quantum sources. We combine global evolutionary optimization (EO) with frequency domain electrodynamical simulations, and compare design strategies based on resonant and non-resonant building blocks. Specifically, we investigate the performance of models with different degrees of freedom but comparable amount of available material. We find that simpler geometric models allow significantly faster convergence of the optimizer, which, expectedly, comes at the cost of a reduced optical performance. We finally analyze the physical mechanisms underlying the directional emission that also comes with an emission rate enhancement, and find a surprising robustness against perturbations of the source emitter location. This makes the structures highly interesting for actual nano-fabrication. We believe that optimized, all-dielectric silicon nano-antennas have high potential for genuine breakthroughs in a multitude of applications in nanophotonics and quantum technologies.Comment: 8 pages, 6 figure

Sondes actives pour l'optique en champ proche à base de nanoparticules isolantes ou de nanodiamants fluorescents

Dans la configuration dite NSOM à ouverture , la résolution optique est dans le meilleur des cas comprise entre 50 et 100 nm. Afin de sonder les propriétés optiques de nanosystèmes, aux dimensions toujours plus petites, une résolution optique plus fine est souhaitable. Pour remplir cet objectif, la solution que nous proposons est l'utilisation d'une sonde active. Une telle sonde repose sur le greffage d'un nano-objet fluorescent à l'apex d'une pointe optique classique. En théorie, la résolution latérale en champ proche devrait être dictée par la taille de ce nano-émetteur (<< 50 nm). Sur la base des travaux réalisés précédemment dans le laboratoire, nous présentons ici deux nouvelles méthodes pour réaliser une telle sonde. Celles-ci impliquent deux types de nanoparticules complémentaires à la taille et aux propriétés optiques attrayantes (forte émission dans le visible, photostabilité). Une première approche a été développée à partir d'un ensemble de nanoparticules de YAG, dopées par des ions cérium, produites et déposées en bout de pointe par LECBD (Low Energy Cluster Beam Deposition). La seconde approche consiste à sélectionner et à fixer en bout de pointe de manière contrôlée (grâce à un polymère) un nanodiamant, contenant des centres colorés (NV), déposé sur une lame de microscopie. L'avancement des travaux est présenté pour les deux types de nano-objets. La mise au point et l'utilisation pour l'imagerie NSOM d'une sonde active à photons uniques, basée sur nanodiamant de 20 nm contenant un seul centre NV et fonctionnant à température ambiante, sont aussi discutées. Au-delà du gain en résolution que peut apporter une telle sonde, ce nouveau type de pointe à photons uniques ouvre de nouvelles perspectives aussi bien en optique et plasmonique quantiques qu'en magnétométrie à haute résolution et haute sensibilité.In the aperture NSOM configuration, the optical resolution is limited to 50-100 nm in the best cases. In order to probe the optical properties of systems which exhibit dimensions at the nanoscale, a better optical resolution would be advantageous. To reach this goal, we suggest the use of an optical active probe. This kind of probe is based on a fluorescent nano-emitter grafted at the apex of a classical dielectric optical probe. The resolution expected in the optical near-field should be ultimately only limited by the size of the nano-object, that is well below 50 nm. On the basis of previous works done in our laboratory, we present here two new methods for obtaining such optical active probes. These new probes involve two complementary kinds of nanoparticles with attractive sizes and good optical properties (like high emission rate in the visible and excellent photostability). The first method implies YAG nanoparticles synthesized and deposited at the apex of a probe using LECBD (Low Energy Cluster Beam Deposition). The second approach is based on the in situ selection of a nanodiamond hosting color centers (NV) which is attached onto the tip with the help of a charged polymer. Finally, we report on the realization of a room-temperature scanning single-photon probe based on a 20 nm nanodiamond hosting a single NV center, which has been successfully used for NSOM imaging. Such tips should ultimately offer a better resolution than classical optical near-field probes, and should also open new perspectives in various fields like quantum optics/plasmonics or high-resolution, high-sensitivity magnetometry.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Near-field microscopy with a single-photon point-like emitter: Resolution versus the aperture tip?

International audienceWe discuss theoretically the concept of spatial resolution in near-field scanning optical microscopy (NSOM) in light of a recent work [Opt. Express 17 (2009) 19969] which reported on the achievement of active tips made of a single ultrasmall fluorescent nanodiamond grafted onto the apex of a substrate tip and on their validation in NSOM imaging. Since fluorescent nanodiamonds tend to decrease steadily in size, we assimilate a nanodiamond-based tip to a point-like single photon source and compare its ultimate resolution with that offered by standard metal-coated aperture NSOM tips. We demonstrate both classically and quantum mechanically that NSOM based on a point-like tip has a resolving power that is only limited by the scan height over the imaged system whereas the aperture-tip resolution depends critically on both the scan height and aperture diameter. This is a consequence of the complex distribution of the electromagnetic field around the aperture that tends to artificially duplicate the imaged objects. We show that the point-like tip does not suffer from this "squint" and that it rapidly approaches its ultimate resolution in the near-field as soon its scan height falls below the distance between the two nano-objects to be resolved

'Deterministic' quantum plasmonics

International audienceWe demonstrate 'deterministic' launching of propagative quantum surface-plasmon polaritons at freely chosen positions on gold plasmonic receptacles. This is achieved by using as plasmon launcher a near-field scanning optical source made of a diamond nanocrystal with two Nitrogen-Vacancy color-center occupancy. Our demonstration relies on leakage-radiation microscopy of a thin homogeneous gold film and on near-field optical microscopy of a nanostructured thick gold film. Our work paves the way to future fundamental studies and applications in quantum plasmonics that require an accurate positioning of single-plasmon sources and may open a new branch in plasmonics and nanophotonics, namely scanning quantum plasmonics

Spectral Tuning of High Order Plasmonic Resonances in Multimodal Film‐Coupled Crystalline Cavities

International audienceSub-micrometric and ultrathin gold cavities sustain several high order planar plasmon resonances in the visible to near infrared spectral window that open new perspectives for the realization of self-assembled metasurfaces or integrated components for nano-optics. This article investigates in detail the far-field spectral features of these multimodal crystalline gold nanoprisms, deposited on either dielectric (glass) or metallic substrates (Au, Al) by dark-field scattering spectroscopy. Relying on the computation of the plasmonic density of states, the signature of each planar resonance is de-convoluted from the experimental global response of single cavities as a function of the cavity size and the substrate nature. The red-shifting dispersion of each resonance is extracted from this decomposition analysis and agrees with predictions from a Green Dyadic Method based numerical tool. In addition, in the presence of 2 a metallic film, we observe a characteristic red or blue shift of the global response for each cavity that results from a metal-specific redistribution of the resonances. The fine spectral tuning of high order plasmonic resonances achieved here reveals the potential of the metal-insulator-metal gap geometry for a static modal engineering within ultrathin gold cavities