HAL Portal IOGS (nstitut d'Optique Graduate School)
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Preirradiation Treatment Influence on the Radioluminescence of a Nitrogen‐Doped Optical Fiber Dosimeter
No full textInternational audienceThe dosimetry performances of a nitrogen‐doped core (diameter of 8 μm) optical fiber, before and after 100 kV X‐Ray preirradiation treatments, up to cumulated dose of 1 MGy(SiO 2 ), to highlight their effects on the radiation‐induced luminescence (RIL), are investigated. The RIL reproducibility versus dose rate calibration curves (in the 0.17–50 Gy s −1 range) are evaluated using four sets of ten different probes: three sets using preirradiated samples at 80 kGy, 280 kGy, 1 MGy, respectively, and one set with pristine samples. The RIL kinetics during ≈60 h long preirradiations at constant dose rate are also studied, showing a non‐negligible bright burn effect. The main outcome is that the preirradiation improves the fiber dosimetry properties since it: 1) enhances fiber radiation detection sensitivity, 2) improves the linearity of the RIL dose rate dependence, and 3) suppresses the observed afterglow postirradiation effect. However, after preirradiation, larger dispersion between the different probes is noted, from 4% (non‐irradiated samples) to 10% for the 1 MGy preirradiated samples. The possible physical explanations are discussed on the basis of the preirradiation filling deep traps that, competing with the RIL centers for the trapping of electrons released by ionization, influence the RIL efficiency
Lasers solides émettant à 2,3 µm à base de cristaux dopés au thulium : Comprendre la spectroscopie pour améliorer l'efficacité
No full textThis thesis focuses on the study of the 3H4 to 3H5 transition of thulium for emission around 2.3 µm in solid-state lasers, with potential applications for molecules detection. As the previous efficiencies and powers reported in the literature are relatively low, various pumping methods have been explored to improve the slope efficiency of these sources, based on an in-depth study of thulium spectroscopy, both from a theoretical and experimental point of view. We began by optimizing conventional pumping at 0.8 µm from the ground state. The benefits of using cascade lasers at 2.3 µm and 1.9 µm were investigated. Under certain conditions, it was possible to double the efficiency of laser emission at 2.3 µm. New crystal host useful for femtosecond lasers, such as CALGO, have also been tested.Secondly, we sought to optimise a new 1 µm upconversion pumping recently demonstrated for laser emission at 2.3 µm. Despite this pumping scheme that at first sight appears to be very inefficient, an order of magnitude gain in terms of efficiency and output power has been demonstrated, putting thulium doped crystal inside a 1-µm neodymium-crystal-based cavity. Both the power emitted and the efficiency now exceed what was ever been demonstrated with a 0.8 µm pumping for the crystals we used. To accompany this power scalling, a study of the thermal effects associated with this emission at 2.3 µm has been carried out. Q-switched lasers at 2.3 µm were also used. Potentially systemic chaos was observed and studied. Various stabilisation processes were proposed.Cette thèse porte sur l'étude de la transition 3H4 vers 3H5 du thulium pour une émission autour de 2,3 µm dans les lasers solides, avec des applications potentielles pour la détection de molécules. Les précédentes efficacités et puissances reportées dans la littérature étant relativement faibles, diverses méthodes de pompage ont été explorées pour améliorer les rendements de ces sources en se basant une étude approfondie de la spectroscopie du thulium, tant d'un point de vue théorique qu'expérimental. Nous avons dans un premier temps tenté d'optimiser le pompage classique à 0,8 µm depuis l'état fondamental. De même, l'intérêt d'utiliser des lasers en cascade à 2,3 µm et à 1,9 µm a été sondé. Dans certaines conditions, il a ainsi été possible de doubler l'efficacité de l'émission laser à 2,3 µm. De nouvelles matrices cristallines utiles pour les lasers femtoseconde telles que le CALGO ont aussi été testées.Dans un second temps, nous avons cherché à optimiser un nouveau pompage à avalanche à 1 µm récemment démontré pour l'émission laser à 2,3 µm. Malgré un schéma de pompage à première vue très peu efficace, un gain d'un ordre de grandeur en terme d'efficacité et de puissance émise a pu être démontré à l'aide d'un pompage intracavité utilisant un laser à néodyme émettant à 1 µm. Tant les puissances émises que les efficacités dépassent aujourd'hui ce qui a été démontré avec um pompage direct à 0,8 µm pour les cristaux que nous avons utilisée. Pour accompagner cette montée en puissance, une étude des effets thermiques liée à cette émission à 2,3 µm a été réalisée. Des lasers déclenchés “Q-switch” à 2,3 µm ont également été étudiés. Un régime chaotique potentiellement systémique a été observé et étudié. Divers processus de stabilisation ont été proposés
Laser-processable high chroma, high angulartolerance color multilayer
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Predicting laser energy absorption on nanostructured surfaces with deep learning
No full textInternational audienceBrief laser pulses can induce autonomous organization of nanostructures pattern without external guidance. This interaction between a laser light and a material is governed by Maxwell's equations. These equations provide the theoretical framework for understanding how electromagnetic waves propagate and interact with matter. The Finite-Difference Time-Domain (FDTD) method models the laser-material interactions, providing insights into absorption, reflection, and scattering over time, ultimately contributing to self-organization within the material. Despite a theoretical understanding, there is no reliable model to predict the self-organization process responsible for the nanostructures. Our work addresses this issue by aiming to predict the surface changes after multiple laser irradiations using neural networks. Deep learning models have undergone advancements and prove suitable for extracting meaningful insights and simulating physical processes. This combination of laser physics and deep learning offer a promising approach to improve our ability to control nanostructures formation on materials
Surfaces nanostructurées par auto-organisation induite par impulsions laser ultrabrèves
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Lâchez les rênes, laissez-vous guider : installation facilitée et sécurisée d'eLabFTW
No full textInternational audienceThe CNRS, a multidisciplinary research institution, launched a service offer in 2023 for the implementation of an electronic laboratory notebook based on an open source tool, eLabFTW. This offer is structured around two solutions : a Cloud SaaS (Software as a Service) offer and an On Premise offer, locally. It is on this On Premise offer that a working group, composed of Bordeaux IT specialists from the RAISIN network attached to the RESINFO federation of Systems and Network Administrators (ASR) profession networks of the Higher Education and Research community, was formed at the end of 2023 to work on a solution project in order to offer support for an on-site deployment. In this article, we will offer you a secure architecture with the details of the configuration steps, while remaining compliant with the technical requirements of the CNRS and current security.Le CNRS, établissement de recherche à caractère pluridisciplinaire, a lancé en 2023 une offre de service pour la mise en place d’un cahier de laboratoire électronique basé sur un outil open source, eLabFTW. Cette offre s’articule autour de deux solutions : une offre Cloud SaaS (Software as a Service) et une offre On Premise, en local. C’est sur cette offre On Premise qu’un groupe de travail, composé d’informaticiens bordelais du réseau RAISIN rattaché à la fédération RESINFO des réseaux de métiers d’Administrateurs Systèmes et Réseaux (ASR) de la communauté Enseignement Supérieur et de la Recherche, s’est constitué fin 2023 pour travailler sur un projet de solution afin de proposer un accompagnement pour un déploiement sur site. Dans cet article, nous allons vous proposer une architecture sécurisée avec le détail des étapes de configuration, tout en restant conforme aux exigences techniques du CNRS et de sécurité en vigueur.</div
The question answering system GeoQA2 and a new benchmark for its evaluation
No full textInternational audienceWe present the question answering engine GeoQA2 which is able to answer geospatial questions over the union of knowledge graphs YAGO2 and YAGO2geo. We also present the dataset GeoQuestions1089 which consists of 1089 natural language questions, their corresponding SPARQL or GeoSPARQL queries and their answers over the union of the same knowledge graphs. We use this dataset to compare the effectiveness of GeoQA2 and the system of Hamzei et al. ( 2022) and make it publicly available to be used by other researchers. Our evaluation shows that although the engine GeoQA2 performs better than the engine of Hamzei et al., both engines have ample room for improvement in their question answering performance
Timing-As-A-Service (TAAS): Over-the-Air Synchronization method for Industrial IoT
No full textInternational audienceThis paper presents a new device model termed as 'Smart Precision Time Protocol (s-PTP) gateway'. This gateway creates a logical interface between the cellular systems (5G, 5G+, etc.) and the Industrial IoT (IIoT) systems. The goal of this gateway is to synchronize IIoT use cases located inside a factory. It is based on a novel business and operational model that we termed as "Timing-As-A-Service (TAAS)". TAAS aims to provide the industrial customers, particularly small and medium businesses, with high precision timing accuracy for Industry 4.0 and future Industry 5.0 use cases. Simulation results illustrate the solution's effectiveness, which shows that the 90th percentile timing error falls below the stringent threshold of 900 ns for IIoT use cases defined by 3GPP, even up to distances of 3km