Conception and elaboration of photonic micro cell for optical references and atomic photonic

Ces travaux portent sur la fabrication et l’optimisation de microcellules photoniques (PMC) à la fois dans le cadre des vapeurs moléculaire comme l’acétylène mais aussi alcaline comme le rubidium. La chaîne de fabrication complète de fabrication y est présentée en partant du design de la fibre creuse où nous avons choisi d’utiliser une fibre hybride tubulaire/Kagomé pour son large coeur, ses faibles pertes et son contenu monomode. Après avoir fabriqué cette fibre, nous présentons un procédé de remplissage et de fermeture avec le gaz souhaité ne souffrant d’aucune source de contamination. Cela nous a permis la fabrication d’une PMC à base d’acétylène présentant de faibles pertes à l’injection et un nouvel état de l’art en terme de pic par spectroscopie d’absorption saturée avec 19MHz de largeur et 30% de contraste. Nous poussons ensuite l’étude de la spectroscopie sub-Doppler en fonction du mode utilisé grâce à la fabrication d’une fibre guidant préférentiellement un mode d’ordre supérieur qui a pour conséquence l’obtention d’un contraste plus élevé et un décalage en fréquence du pic de transparence. Le deuxième axe de cette thèse tente d’appliquer aux vapeurs alcalines les procédés précédents et d’autre pour aller vers la première PMC totalement fibrée à vapeur de rubidium. Parmi ces pistes, on note l’utilisation de revêtements intra-fibre qui permettent de limiter l’adsorption du rubidium et sa réactivité ou encore améliorant ses propriété anti-relaxantes. La caractérisation de ces dépôts sur les parois du coeur de fibres creuses a été réalisée intra-fibre par une mesure de la relaxation de polarisation.This work focuses on the fabrication and optimization of photonic microcells (PMCs) both in the context of molecular vapors such as acetylene but also alkaline such as rubidium. The complete production chain is presented there, starting from the hollow fiber design where we have chosen to use a tubular / Kagomé hybrid fiber for its large core, low losses and single mode content. After fabricating this fiber, we present a process for filling and closing with the desired gas that does not suffer from any source of contamination. This allowed us to manufacture an acetylene-based PMC with low injection losses and a new state of the art in terms of SAS peak with 19MHz of width and 30% of contrast. We then push the study of sub- Doppler spectroscopy according to the mode used thanks to the manufacture of a fiber preferentially guiding a higher order mode. It results in obtaining a higher contrast and a shift in frequency of the transparency peak. The second axis of this thesis attempts to apply to alkaline vapors the developed processes as well as another to tend to the first completely sealed PMC based on rubidium. Among these avenues, we note the use of in-fiber coating, which makes it possible to limit the adsorption of rubidium, its reactivity, or even having anti-relaxing properties. The characterization of these deposits on the walls of the hollow fiber core is in-fiber carried out with the observation of the polarization relaxation

Characterization and modelling of solidification structures in GTAW of austenitic alloys

La nécessité de garantir l’intégrité des structures soudées pousse les industriels à augmenter leur domaine de compétences en matière de simulation numérique du soudage. La solidification est l’étape clé de ce procédé. Dès lors que la sélection des grains est reproduite correctement par les simulations, le comportement mécanique et la réponse aux contrôles non destructifs de l’assemblage peuvent être déduits. Ce travail cherche à définir les phénomènes thermométallurgiques décrivant les mécanismes de formation des microstructures du soudage. Ces mécanismes servent ensuite à valider l’usage d’un nouveau modèle de solidification qui réalise un post-traitement du calcul de thermique avec un automate cellulaire (modèle CAFE_WELD). Pour se faire, des expériences de soudage sont réalisées et caractérisées par EBSD. Ces analyses permettent de suivre la sélection des grains dans la soudure. L’effet de la refusion sur la sélection des grains est bien mis en évidence lors du soudage multi-passes. Ces caractérisations sont complétées par une analyse fine de la solidification du métal d’apport utilisé pour le soudage. Ces résultats permettent la mise en données du modèle nécessaire à la réalisation numérique des mêmes expériences de soudage. Les comparaisons entre les soudures vraies et numériques montrent que les phénomènes physiques intégrés au modèle ne sont pas suffisants pour reproduire les propriétés microstructurales générées par le soudageToday, industrials want to upgrade their welding numerical simulation knowledge’s in order to be able to guarantee the welded structure integrity. Solidification is the main step of welding process. As soon as the grain selection in welded region is well reproduced by simulation software, mechanical properties and nondestructive test response can be deduced. This work tries to find thermometallurgical phenomena in order to describe the microstructures formation during welding. These mechanisms are used for validating a new solidification model which realizes a thermal calcul post-treatment with a cellular automaton (CAFE_WELD). In this aim, welding experiences were done and characterized with EBSD. These analyses allow following the grain selection into the weld. The refusion effect is clearly seen in the case of multi-pass weld. These results are completed by the fine solidification characterizations on filler metal employed in welding experiences. In this way, the model implementation can be done in order to do numerical simulation of the same experiences. The comparisons between real and numerical experiences show that the physical laws taken into account in CAFE_WELD model are not sufficient to reproduce the microstructural properties occurring in weldin

Caractérisation et modélisation des structures de solidification en soudage TIG d’alliages austénitiques

Today, industrials want to upgrade their welding numerical simulation knowledge’s in order to be able to guarantee the welded structure integrity. Solidification is the main step of welding process. As soon as the grain selection in welded region is well reproduced by simulation software, mechanical properties and nondestructive test response can be deduced. This work tries to find thermometallurgical phenomena in order to describe the microstructures formation during welding. These mechanisms are used for validating a new solidification model which realizes a thermal calcul post-treatment with a cellular automaton (CAFE_WELD). In this aim, welding experiences were done and characterized with EBSD. These analyses allow following the grain selection into the weld. The refusion effect is clearly seen in the case of multi-pass weld. These results are completed by the fine solidification characterizations on filler metal employed in welding experiences. In this way, the model implementation can be done in order to do numerical simulation of the same experiences. The comparisons between real and numerical experiences show that the physical laws taken into account in CAFE_WELD model are not sufficient to reproduce the microstructural properties occurring in weldingLa nécessité de garantir l’intégrité des structures soudées pousse les industriels à augmenter leur domaine de compétences en matière de simulation numérique du soudage. La solidification est l’étape clé de ce procédé. Dès lors que la sélection des grains est reproduite correctement par les simulations, le comportement mécanique et la réponse aux contrôles non destructifs de l’assemblage peuvent être déduits. Ce travail cherche à définir les phénomènes thermométallurgiques décrivant les mécanismes de formation des microstructures du soudage. Ces mécanismes servent ensuite à valider l’usage d’un nouveau modèle de solidification qui réalise un post-traitement du calcul de thermique avec un automate cellulaire (modèle CAFE_WELD). Pour se faire, des expériences de soudage sont réalisées et caractérisées par EBSD. Ces analyses permettent de suivre la sélection des grains dans la soudure. L’effet de la refusion sur la sélection des grains est bien mis en évidence lors du soudage multi-passes. Ces caractérisations sont complétées par une analyse fine de la solidification du métal d’apport utilisé pour le soudage. Ces résultats permettent la mise en données du modèle nécessaire à la réalisation numérique des mêmes expériences de soudage. Les comparaisons entre les soudures vraies et numériques montrent que les phénomènes physiques intégrés au modèle ne sont pas suffisants pour reproduire les propriétés microstructurales générées par le soudag

Autoimmune thrombotic thrombocytopenic purpura associated with disseminated sarcoidosis: A case report

Abstract Sarcoidosis is an inflammatory disease known to be associated with multiple autoimmune disorders. There is a restricted number of descriptions of the association between sarcoidosis and autoimmune thrombotic thrombocytopenic purpura (aTTP). We present the case of a 63‐year‐old woman admitted to the hospital to investigate a possible sarcoidosis who had hemolytic anemia and thrombocytopenia, with low ADAMTS13 activity and anti‐ADAMTS13 antibodies, leading to a diagnosis of aTTP. Sarcoidosis was later confirmed and the two conditions evolved separately after 6 months, questioning the link between them. Clinicians should be aware of this rare cause of thrombocytopenia in patients with sarcoidosis, as aTTP is a life‐threatening condition

Saturated absorption spectroscopy using azimuthally structured mode in hollow-core fiber

International audienceWe report on transversally structured beam effect on saturated absorption spectroscopy in acetylene-filled hollow-core fiber. Experimental results reveal frequency shift and contrast enhancement of absorption lines using LP11 guided mode rather than gaussian-like mode. © 2022 The Author(s) Sub-Doppler spectroscopy such as electromagnetically induced transparency (EIT) or saturated absorption spectroscopy (SAS) is usually performed with a Gaussian mode profile both in free-space and guided optics configurations. Recently, in free space, works have been reported where Laguerre-Gaussian (LG) modes have been set as pump or probe beams in EIT [1-5] and SAS [6] schemes in Rb vapors. Radial variation of LG mode induces narrowing of Doppler-free transparencies profiles. Chanu et al. [1] demonstrated decrease of resonances linewidths of Rb of almost factor 6 switching from Gaussian to LG mode. For [5], LG modes contribute to increase the Rb Zeeman level lifetime and so decrease the FWHM. Furthermore, influence of LG modes order has also been studied in [2] demonstrating that larger order induces narrower signal due to its azimuthal component and authors of [4] present the influence of transverse mode overlap (pump and probe) on the signal. Gas-filled HCPCF technology already demonstrated its potential and impact on the enhancement of the light-gas interactions phenomena and especially in spectroscopy. The various works deriving from the seminal demonstration [7] have been limited to pump (or pump-probe) Gaussian beam configurations due to the fact that most of the developments on HCPCFs have been focused on the design and fabrication of fibers supporting the lowest loss LP01 like mode with the main objective to increase transmission performances. Moreover, the intrinsic cladding modal properties of microstructured hollow-core fibers render difficult the control on the loss mode hierarchy and to guide light in a high order single mode fashion. This restriction has been lifted by the emergence of the tubular cladding HCPCF providing a large flexibility on the tubes cladding position. Thanks to alteration of the azimuthal position of the cladding tubes, Osorio et al. [8] demonstrated, theoretically and experimentally, for the first time in a HCPCF, an inversion of the classical loss hierarchy in fibers developing fibers whose lowest loss modes are the LP11 and LP21, instead of the LP01. In this study, we specifically design and fabricate a fiber based on this geometry allowing to guide preferentially high order mode (HOM) around 1550nm without any specific light coupling precaution, we report for the first time to the best of our knowledge on SA spectroscopy generated in HCPCF with a LP11 high-order mode control beam. Comparison with Gaussian control beam configuration demonstrates an increase of the contrast and peak position shift

Solution-based deposition of ceramics on glass substrates for alkali-metal vapor cells

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Microsegregation Model Including Convection and Tip Undercooling: Application to Directional Solidification and Welding

International audienceThe microsegregation behavior of alloy filler metal 52 (FM 52) was studied using microprobe analysis on two different solidification processes. First, microsegregation was characterized in samples manufactured by directional solidification, and then by gas tungsten arc welding (GTAW). The experimental results were compared with Thermo-Calc calculations to verify their accuracy. It was confirmed that the thermodynamic database predicts most alloying elements well. Once this data had been determined, several tip undercooling calculations were carried out for different solidification conditions in terms of fluid flow and thermal gradient values. These calculations allowed the authors to develop a parametrization card for the constants of the microsegregation model, according to the process parameters (e.g., convection in melt pool, thermal gradient, and growth velocity). A new model of microsegregation, including convection and tip undercooling, is also proposed. The Tong-Beckermann microsegregation model was used individually and coupled with a modified Kurz-Giovanola-Trivedi (KGT) tip undercooling model, in order to take into account the convection in the fluid flow at the dendrite tip. Model predictions were compared to experimental results and showed the microsegregation evolution accurately

Contaminant-free end-capped and single-mode acetylene photonic microcell for sub-Doppler spectroscopy

International audienceWe report on the development of an acetylene-filled photonic microcell based on an assembly process that is contaminant free and requires no helium buffer gas nor gluing procedure. The microcell consists of a 7-m-long and 30 µm core-diameter inhibited-coupling guiding hollow-core photonic crystal fiber filled with acetylene gas at a pressure in the range of 80 µbar, sealed by capping its ends with fusion-collapsing a glass-tube sleeve, and mounted on FC connectors for integration. The microcell shows a robust single-mode behavior and a total insertion loss of ∼1.5dB. The spectroscopic merit of the formed microcell is tested by generating electromagnetic induced transparency and saturated absorption on R13 and P9 absorption lines, respectively. The sub-Doppler transparencies show a close to transit time limited linewidth of 17±3MHz. The latter was monitored for over 3 months. As a demonstration, the microcell was used to frequency stabilize a laser with fractional frequency instability improvement by a factor 50 at 100 s integration time compared to free running laser operation

Contaminant free end-capped acetylene PMC for sub-Doppler spectroscopy

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