Dans un laboratoire de nanosciences

An english version of this article is available (http://arxiv.org/abs/1105.5566) and will be published in the C.R. Physique in a dossier devoted to the merits and risks of Nanotechnologies.La fabrication, l'observation et la manipulation d'objets très petits est un tour de force, mais ces objets, susceptibles de s'infiltrer partout sans être perçus, peuvent susciter la méfiance. Pour mieux apprécier la situation, nous décrivons l'activité d'un institut de recherche spécialisé dans les nanosciences, certaines des méthodes qui y sont utilisées, l'esprit de ses chercheurs et leur attitude vis à vis des risques. An english version of this article is available (http://arxiv.org/abs/1105.5566) and will be published in the C.R. Physique in a dossier devoted to the merits and risks of Nanotechnologies

In a nanoscience lab

The production, observation and manipulation of very small objects is a tour de force, but these objects, which could infiltrate anywhere without being seen, may arouse suspicion. To assess the situation at best, we describe the activity of a nanoscience research institution, some of the methods used there, the spirit of its researchers and their attitude towards risk.Comment: article accept\'e pour publication dans les C.R. Physique. El\'ement d'un dossier 'Nanosciences et nanotechnologies: esp\'erances et inqui\'etudes". D'autres articles de ce dossier, ainsi que la version fran\c{c}aise de cet articles, seront \'egalement soumis \`a HA

Degenerate epitaxy-driven defects in monolayer silicon oxide onto ruthenium

The structure of the ultimately-thin crystalline allotrope of silicon oxide, prepared onto a ruthenium surface, is unveiled down to atomic scale with chemical sensitivity, thanks to high resolution scanning tunneling microscopy and first principle calculations. An ordered oxygen lattice is imaged which coexists with the two-dimensional monolayer oxide. This coexistence signals a displacive transformation from an oxygen reconstructed-Ru(0001) to silicon oxide, along which latterally-shifted domains form, each with equivalent and degenerate epitaxial relationships with the substrate. The unavoidable character of defects at boundaries between these domains appeals for the development of alternative methods capable of producing single-crystalline two-dimensional oxides

Fabrication et étude optique de microcavités à modes de galerie intégrées sur silicium

Ce travail de thèse a consisté à mettre en place toute une filière de fabrication de microtores en silice sur silicium (étapes de lithographie et de gravure en salle blanche pour la réalisation de microdisques, installation d'un banc optique permettant la transformation du résonateur en microtore par un procédé de recuit laser CO2), à installer un banc optique permettant de mesurer la largeur spectrale de leurs résonances optiques à 1.55 m et enfin, à explorer l'intégration d'émetteurs de lumière composés d'éléments de la colonne IV comme du silicium et du germanium, dans ces cavités. Des microtores supportant des résonances de facteur de qualité Q proche de 10^8 à 1.55 m ont été fabriqués. Ces réalisations sont très proches de l'état de l'art et valident à la fois la fabrication des cavités et le banc optique permettant les mesures spectrales des modes de galerie (WGM). Grâce à un contrôle fin des différentes étapes de fabrication, de nouveaux résonateurs ont également été réalisés, des microsphères de silice sur puce de petits rayons (entre 5 et 14 m). Une étude détaillée de ces résonateurs est présentée. Des Q proches de 10^8 ont également été mesurés. Des cavités WGM comportant une couche de nanoclusters de silicium dans une matrice de silice avec des ions erbium (SiOx : Er) sont étudiées en photoluminescence. Un couplage des ces émetteurs à des WGM est observé à température ambiante dans le visible et dans l'infrarouge. Un travail de couplage du germanium aux WGM a commencé et semble prometteur.This work consisted in developing a fabrication process of silica microtoroids on a silicon chip (steps of lithography and etching in clean room for the realization of microdisks, set up of an optical bench to form a microtoroid with a reflow treatment of a silica microdisk by a CO2-laser), setting up an optical bench to measure the linewidth of their optical resonances at 1.55 m and finally, exploring light emitters integration in these cavities such as silicon and germanium. Very high quality-factors (Q) close to 10^8 at 1.55 m have been measured on microtoroids. These realizations are very close to the State of the art and validate both the fabrication of these cavities and the optical bench to measure the linewidth of their Whispering Gallery Modes (WGM). With a precise control of the fabrication steps, new resonators have also been fabricated, silica microspheres on a chip with small radii (5 < r < 14 m). An in-depth study of these last ones is presented. Q-factors close to 10^8 have also been measured on microspheres. WGM cavities with a SiOx: Er layer (silicon nanoclusters in silica with erbium ions) are studied by photoluminescence. Coupling of these light emitters to WGM is observed in visible and near infrared at room temperature. A work of coupling of germanium to WGM began and seems promising.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Near-field spectroscopy of low-loss waveguide integrated microcavities

International audienceA scanning near-field spectroscopy method is used to observe loss reduction and Q-factor enhancement due to transverse-mode profile matching within photonic-crystal microcavities. Near-field measurements performed directly on cavity modes are compared with three-dimensional calculations and quantitative agreement is observed. (c) 2006 American Institute of Physics

Photonics at nanometer scale: tracking light in high Q low V nanocavities

Photonic crystals (PCs) have proven to be an efficient way to tightly confine the electromagnetic field in nanocavities or slow down light propagation within optical waveguides. Very recently it has been proposed to use a nanometric optical probe to observe in near-field the light confinement and propagation within PC devices. In this work we analyze the optical properties of PC nanostructures by using a SNOM probe in collection mode in association with transmission measurements. We also explore the possibility to use the nanometric tip for a new class of Near-field Optics Nanometric Silicon Systems (NONSS) dedicated to on-chip information routing and processing. In a first step, we show that with to the SNOM probe it is possible to evidence different light behaviours depending on optical mode profile. Mode coupling in PC waveguides and quality factor changes in PC nanocavities will be discussed. Then in a second step, we show that strong field confinement enhancement can be achieved in nanocavities by proper mirror designs including mode matching and losses recycling. A quality factor (Q) enhancement by two orders of magnitude is observed. These experimental results are discussed in light of numerical calculations. Finally, in a third step, we fabricated a nanocavity in a monomode SOI ridge waveguide with an ultimately low microcavity modal volume of 0.6(l/n)^3. We use this high-Q low-V nanocavity to explore the nanocavity - nanometric optical probe interaction

Room-temperature optically pumped CdHgTe vertical-cavity surface-emitting laser for the 1.5 μm range

International audienc

2.6 μm optically pumped vertical-cavity surface-emitting laser in the CdHgTe system

International audienc

Resonant cavity light emitting diodes for the 3–5 μm range

International audienc