Erbium-doped nanoparticles in silica-based optical fibres

Developing of new rare-earth (RE)-doped optical fibres for power amplifiers and lasers requires continuous improvements in the fibre spectroscopic properties (like shape and width of the gain curve, optical quantum efficiency, resistance to spectral hole burning and photodarkening...). Silica glass as a host material for fibres has proved to be very attractive. However, some potential applications of RE-doped fibres suffer from limitations in terms of spectroscopic properties resulting from clustering or inappropriate local environment when doped into silica. To this aim, we present a new route to modify some spectroscopic properties of RE ions in silica-based fibres based on the incorporation of erbium ions in amorphous dielectric nanoparticles, grown in-situ in fibre preforms. By adding alkaline earth elements, in low concentration into silica, one can obtain a glass with an immiscibility gap. Then, phase separation occurs under an appropriate heat treatment. We investigated the role of three alkaline-earth elements: magnesium, calcium and strontium. We present the achieved stabilisation of nanometric erbium-doped dielectric nanoparticles within the core of silica fibres. We present the nanoparticle dimensional characterisation in fibre samples. We also show the spectroscopic characterisation of erbium in preform and fibre samples with different compositions. This new route could have important potentials in improving RE-doped fibre amplifiers and laser sources.Comment: arXiv admin note: text overlap with arXiv:1201.111

Fabrication of Rare Earth-Doped Transparent Glass Ceramic Optical Fibers by Modified Chemical Vapor Deposition

Rare earth (RE) doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of post-ceramming. The main characteristics of the RE-doped oxyde nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline earth element used as phase separating agent. Magnesium and erbium co-doped fibers were fabricated. Optical transmission in term of loss due to scattering as well as some spectroscopic characteristics of the erbium ions was studied. For low Mg content, nano-scale particles could be grown with and relatively low scattering losses were obtained, whereas large Mg-content causes the growth of larger particles resulting in much higher loss. However in the latter case, certain interesting alteration of the spectroscopic properties of the erbium ions were observed. These initial studies should be useful in incorporating new doped materials in order to realize active optical fibers for constructing lasers and amplifiers

Risk assessment of SARS-CoV-2 infection in free-ranging wild animals in Belgium.

The aim of this review paper is to evaluate the putative susceptibilities of different free-ranging wild animal species in Belgium to SARS-CoV-2 and provide a risk assessment of SARS-CoV-2 infection in those animals. Since the onset of the Covid-19 pandemic, natural SARS-CoV-2 infections have mainly been confirmed in domestic and production animals, and in wild animals kept in captivity, although the numbers remain limited when compared to human cases. Recently, the first SARS-CoV-2 infections in presumably escaped minks found in the wild have been detected, further addressing the much-feared scenario of transmission of the virus to animals living in the wild and its consequences. Considering the most likely origin of the virus being a wild animal and the putative susceptibilities of free-ranging wild animal species to SARS-CoV-2, the risk of infection with possible establishment of the virus in these populations has to be investigated closely. The authors conclude that most attention should be given to surveillance and awareness raising activities for SARS-CoV-2 infection in wild mustelids, bats, wild canids and felids, particularly these collected in wildlife rescue centres. People involved in frequent and close contact with wild animals should take all necessary precautionary measures to protect wild animals against exposure to the virus. One year after the first detection of SARS-CoV-2 in humans, the time has come to increase investments in research and surveillance activities in animals, including in free-ranging wild animals, as part of a One Health control of this pandemic. This study focusing on Belgium could be helpful for other countries with similar animal densities and ecosystems

Formes du réel et de l'irréel dans les propositions finales en anglais

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Formes du réel et de l'irréel dans les propositions finales en anglais

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Élaboration de fibres optiques nanostructurées dopées aux ions de terres rares (influence des paramètres de fabrication sur la synthèse et la croissance des nanoparticules)

Les fibres optiques dopées aux ions erbium sont utilisées pour réaliser des amplificateurs. Dans un objectif de contrôler et de modifier les propriétés spectroscopiques de l erbium dans ces fibres optiques à base de silice, nous étudions une voie originale consistant à encapsuler ces ions dans des nanoparticules d oxyde obtenues in-situ directement au cours du procédé MCVD. La modification de l environnement local de l erbium permet de modifier les propriétés spectroscopiques. Ces nanoparticules apparaissent au cours de la fabrication grâce à l incorporation d un agent nucléant. Les cycles thermiques nécessaires à la fabrication de la préforme permettent alors de déclencher une séparation de phases spontanée. Cette thèse a pour but d étudier l influence des différents paramètres de fabrication (concentration en agent nucléant dans la solution de dopage, phases de consolidation ou de rétreint, etc.) sur les caractéristiques des nanoparticules et les propriétés spectroscopiques de l erbium. L étude des paramètres est regroupée dans ce manuscrit suivant deux axes : composition du matériau et cycles thermiques. Les nanoparticules ont été principalement caractérisées par Microscopie Electronique à Balayage (MEB). La spectroscopie de l erbium a été analysée en réalisant des mesures de spectres d émission et de temps de vie de la fluorescence à 1,5 m. Des modifications spectroscopiques (élargissement de 40 à 60% de la largeur à mi-hauteur du spectre d émission) ont été obtenues seulement pour les fibres présentant des diamètres moyens de particule élevés (50 nm). Les critères de transparence de pourront donc être satisfaits qu en jouant sur la densité de particules.Erbium-doped optical fibres are commonly used to realize amplifiers. To control and modify erbium spectroscopic properties in these silica-based optical fibres we study an original way that consists in encapsulating ions into oxide nanoparticles obtained in-situ, directly during MCVD process. The modification of the erbium local environment allows to modify spectroscopic properties. These nanoparticles appear during the fabrication with the incorporation of a nucleation agent. Thermal cycles necessary to the perform fabrication ensure therefore to activate a spontaneous phase separation? This thesis aims to study the effect of different fabrication parameters, such as nucleating agent concentration in the doping solution or consolidation and collapsing phases, on the nanoparticle characteristics and erbium spectroscopic properties. In this manuscript, this study of the different parameters is organised in two axes : material composition an thermal cycles. Nanoparticles have mainly been characterised by Scanning Electron Microscopy (SEM). Erbium spectroscopy has been analysed by means of emission spectrum measurements as well as measurements of the 1,5 m fluorescence lifetime. Spectroscopic modifications, i. e. emission spectrum broadening of 40 until 60 %, have only been obtained for fibres that exhibit particles with high mean diameters (50 nm). Transparency criteria could only be satisfied while manipulating particle density.NICE-BU Sciences (060882101) / SudocSudocFranceF

Les attentes des salariés de la région Nord- Pas de Calais en matière d’ARTT: synthèse et conclusions

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Interplay between thermal transfers and degradation of the bronchial epithelium during exercise

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