2,357 research outputs found
Stratégies de réalisation de guides polymÚres pour la modulation électro-optique à haut débit
National audienceDe nouveaux polymĂšres Ă©lectro-optiques, sont mis en Ćuvre pour rĂ©aliser des guides selon deux types d'ingĂ©nierie de matĂ©riaux. L'une consiste Ă utiliser un polymĂšre non-linĂ©aire greffĂ© et rĂ©ticulable et l'autre utilise un matĂ©riau hĂŽte, ayant une tempĂ©rature de transition vitreuse Ă©levĂ©e. Nous prĂ©sentons ici, les difficultĂ©s rencontrĂ©es lors de la rĂ©alisation des guides et les stratĂ©gies dĂ©veloppĂ©es pour aboutir, avec ces nouveaux matĂ©riaux, Ă des guides optiques monomodes
Micro-resonators based on integrated polymer technology for optical sensing
International audienceResearch on sensors has experienced a noticeable development over the last decades especially in label free optical biosensors. However, compact sensors without markers for rapid, reliable and inexpensive detection of various substances induces a significant research of new technological solutions. The context of this work is the development of a sensor based on easily integrated and inexpensive micro-resonator (MR) component in integrated optics, highly sensitive and selective mainly in the areas of health and food. In this work, we take advantage of our previous studies on filters based on micro-resonators (MR) to experiment a new couple of polymers in the objective to use MR as a sensing function. MRs have been fabricated by processing SU8 polymer as core and PMATRIFE polymer as cladding layer of the waveguide. The refractive index contrast reaches 0.16 @ 1550 nm. Sub-micronic ring waveguides gaps from 0.5 to 1 ”m have been successfully achieved with UV (i-line) photolithography. This work confirms our forecasts, published earlier, about the resolution that can be achieved. First results show a good extinction coefficient of ~17 dB, a quality factor around 104 and a finesse of 12. These results are in concordance with the theoretical study and they allow us to validate our technology with this couple of polymers. Work is going on with others lower cladding materials that will be used to further increase refractive index contrast for sensing applications
Analyse des pertes optiques dans les guides polymĂšres
National audienceLes guides polymĂšres peuvent prĂ©senter des pertes optiques trĂšs diffĂ©rentes suivant les matĂ©riaux mis en jeux et les technologies utilisĂ©es. Il est donc important de pouvoir distinguer entre ce qui est inhĂ©rent strictement au matĂ©riau, les pertes intrinsĂšques, et, ce qui relĂšve de la technologie de fabrication des guides, les pertes extrinsĂšques, afin d'optimiser au mieux la propagation dans ces circuits optiques. A l'aide de diffĂ©rentes techniques de mesure dĂ©veloppĂ©es au laboratoire, nous essayons dans cet article de cerner les pertes limites de ces matĂ©riaux en nous appuyant aussi, sur des mesures expĂ©rimentales de guides dont nous maitrisons la technologie de mise en Ćuvre
Capteur en Optique Intégrée à Base de Verres de Chalcogénures pour la Détection de Polluants dans le Moyen-Infrarouge
National audienceLe Moyen Infra-Rouge (MIR) est la rĂ©gion spectrale comprise entre 3 et 20 ”m. Cette gamme de longueurs dâonde est connue pour contenir des transitions vibrationnelles fondamentales caractĂ©ristiques dâespĂšces molĂ©culaires en phase liquide ou gazeuse. De nombreuses substances telles que le toluĂšne, le mĂ©thanol, lâĂ©thanol, lâacĂ©tone, le glucose, le dioxyde de carbone peuvent ĂȘtre caractĂ©risĂ©es par spectroscopie infrarouge grĂące Ă leur signature spectrale dâabsorption. Cette technique est ainsi une des plus appropriĂ©es parmi les techniques classiques dâanalyse pour lâidentiïŹcation et la caractĂ©risation structurelle des espĂšces molĂ©culaires. Les disponibilitĂ©s rĂ©centes de plateformes optiques prĂ©sentant de faibles pertes de propagation et de sources Ă©mettant dans le MIR, notamment des QCL ont Ă©tĂ© la clĂ© du dĂ©veloppement dâĂ©tudes destinĂ©es Ă la rĂ©alisation de capteurs optiques fonctionnant dans la gamme spectrale du MIR. Par ailleurs, les capteurs en optique intĂ©grĂ©e sont devenus une excellente alternative pour la dĂ©tection in situ car ils prĂ©sentent certains avantages sur les autres types de capteurs, tels que l'intĂ©gration des Ă©lĂ©ments dans un dispositif compact. Ils sont actuellement utilisĂ©s dans divers domaines sociĂ©taux tels que la santĂ©, la dĂ©fense et lâenvironnement.Il existe diffĂ©rents matĂ©riaux transparents dans le MIR (le silicium, le germanium, lâarsĂ©niure de galium ou encore les verres de chalcogĂ©nures) susceptibles de constituer la plateforme optique de ces capteurs intĂ©grĂ©s. Les verres de chalcogĂ©nures (ChGs) sont des matĂ©riaux semi-conducteurs composĂ©s par les Ă©lĂ©ments du groupe VIa (sĂ©lĂ©nium (Se), tellure (Te) ou soufre (S)). Ils forment des verres lorsquâils sont mĂ©langĂ©s Ă un ou plusieurs autres Ă©lĂ©ments tels que le galium (Ga), le germanium (Ge), lâantimoine (Sb), le silicium (Si) ou le phosphore (P). Ces verres de ChGs se distinguent par leur transparence Ă©tendue dans lâinfrarouge: certaines compositions transmettent jusquâĂ 20 ”m. Typiquement, leur transmission dans le MIR a Ă©tĂ© caractĂ©risĂ©e jusquâĂ 12 ”m pour les sulfures, Ă 16 ”m pour les sĂ©lĂ©niures et Ă 18 ”m pour les tellures. Certains travaux ont montrĂ© la fabrication et la caractĂ©risation de capteurs optiques dans le proche infra-rouge. Dans cet article, nous proposons de tirer profit de la transparence Ă©levĂ©e de ces matĂ©riaux dans le MIR pour fabriquer un capteur spectroscopique Ă onde Ă©vanescente fonctionnant dans cette gamme spectrale.
Technologie d'optique intégrée polymÚre au laboratoire FOTON
National audienceCet article résume le panorama de l'état de l'art des technologies d'optique intégrée polymÚre maitrisées au laboratoire Foton (SystÚmes Photoniques) et qui sont axées sur des circuits optiques actifs et passifs. Les objectifs sont orientés vers un fort confinement du mode de propagation, la génération d'effets non linéaires, l'hybridation avec d'autres matériaux et la réduction des pertes (couplage et propagation)
Search for supersymmetry in events with opposite-sign dileptons and missing transverse energy using an artificial neural network
In this paper, a search for supersymmetry (SUSY) is presented in events with two opposite-sign isolated leptons in the final state, accompanied by hadronic jets and missing transverse energy. An artificial neural network is employed to discriminate possible SUSY signals from a standard model background. The analysis uses a data sample collected with the CMS detector during the 2011 LHC run, corresponding to an integrated luminosity of 4.98ââfb-1 of proton-proton collisions at the center-of-mass energy of 7 TeV. Compared to other CMS analyses, this one uses relaxed criteria on missing transverse energy (EÌžT>40ââGeV) and total hadronic transverse energy (HT>120ââGeV), thus probing different regions of parameter space. Agreement is found between standard model expectation and observations, yielding limits in the context of the constrained minimal supersymmetric standard model and on a set of simplified model
Achieving coordinated national immunity and cholera elimination in Haiti through vaccination: a modelling study
Summary: Background: Cholera was introduced into Haiti in 2010. Since then, more than 820â000 cases and nearly 10â000 deaths have been reported. Oral cholera vaccine (OCV) is safe and effective, but has not been seen as a primary tool for cholera elimination due to a limited period of protection and constrained supplies. Regionally, epidemic cholera is contained to the island of Hispaniola, and the lowest numbers of cases since the epidemic began were reported in 2019. Hence, Haiti may represent a unique opportunity to eliminate cholera with OCV. Methods: In this modelling study, we assessed the probability of elimination, time to elimination, and percentage of cases averted with OCV campaign scenarios in Haiti through simulations from four modelling teams. For a 10-year period from January 19, 2019, to Jan 13, 2029, we compared a no vaccination scenario with five OCV campaign scenarios that differed in geographical scope, coverage, and rollout duration. Teams used weekly department-level reports of suspected cholera cases from the Haiti Ministry of Public Health and Population to calibrate the models and used common vaccine-related assumptions, but other model features were determined independently. Findings: Among campaigns with the same vaccination coverage (70% fully vaccinated), the median probability of elimination after 5 years was 0â18% for no vaccination, 0â33% for 2-year campaigns focused in the two departments with the highest historical incidence, 0â72% for three-department campaigns, and 35â100% for nationwide campaigns. Two-department campaigns averted a median of 12â58% of infections, three-department campaigns averted 29â80% of infections, and national campaigns averted 58â95% of infections. Extending the national campaign to a 5-year rollout (compared to a 2-year rollout), reduced the probability of elimination to 0â95% and the proportion of cases averted to 37â86%. Interpretation: Models suggest that the probability of achieving zero transmission of Vibrio cholerae in Haiti with current methods of control is low, and that bolder action is needed to promote elimination of cholera from the region. Large-scale cholera vaccination campaigns in Haiti would offer the opportunity to synchronise nationwide immunity, providing near-term population protection while improvements to water and sanitation promote long-term cholera elimination. Funding: Bill & Melinda Gates Foundation, Global Good Fund, Institute for Disease Modeling, Swiss National Science Foundation, and US National Institutes of Health
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