HAL Portal IOGS (nstitut d'Optique Graduate School)
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Self-regulating and self-oscillating metal-organic framework hybrid plasmonic metasurfaces
No full textInternational audienceMetal-organic frameworks (MOFs) offer remarkable chemical versatility, structural diversity, and, in some cases, stimuli-responsiveness. In the latter case, they typically rely on external inputs to trigger these changes. In contrast, living systems possess the ability to internally self-regulate and autonomously adapt their properties without external intervention, utilizing internal feedback mechanisms. To fill this gap, we develop a MOF-based metasurface that exhibits autonomous optical self-regulation, dynamically adjusting light absorption in response to varying incident light intensity. This device integrates colloidal MOFs with a plasmonic metasurface to create a thermo-optical negative feedback mechanism based on vapor sorption in and out of the colloidal MOF device. The self-regulation process is dynamic, leading each MOF/antenna unit to exhibit self-oscillatory behavior in the presence of a constant external energy input, analogous to a light-fueled nanoscale steam engine. This proof-of-concept highlights the potential of harnessing MOFs and sorption processes for designing metasurfaces for adaptable optical applications. It also represents a first step toward the design of materials integrating feedback mechanisms and internal clocks paving the way for a new generation of porous materials with life-like autonomy
Unveiling localized plasmonic activation comparing photochemically and thermally initiated polymerization
No full textIn this paper, we introduce a chemical approach to spatially investigate the energy transfer around nanoparticles excited by fs-pulsed illumination in near-infrared. Free radical acrylate polymers that can crosslinked either by photochemical or thermal pathway are used under the same illumination conditions on gold nanotriangles. The objective is to disentangle between photoinduced and thermal polymerization using the same acrylate chemistry. In photochemical regime, local photopolymerization is observed at the apex of the nanotriangles with spatial control depending on the excitation polarization. For the thermal polymer, at moderate power, nanometer-sized polymer lobes are observed on the apexes of the triangle, their position depending also on the direction of polarization. At higher power, anisotropic melting of the gold within the gold nanotriangles was observed, also depending on incident light polarization. These results are compared with theoretical calculations using modified three-temperature model, to study the nanotriangle particles time and space heat distribution. This new methodology reveals that ultrafast (< 300 fs) energy exchange can occur between the nanoparticle and the surrounding medium before temperature homogenization within the nanoparticle. Our results demonstrate the possibility to generate extremely localized nanoscale energy sources able to trigger thermal chemical reactions. We discuss the possible mechanisms beyond this energy transfer. This fundamental breakthrough opens up many new perspectives in nanofabrication based on thermally polymerizable formulations
Mixed Neutron and Gamma Effects on Optical Fibers and Coating Materials
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Western diet since adolescence impairs brain functional hyperemia at adulthood in mice: rescue by a balanced ω-3:ω-6 polyunsaturated fatty acids ratio
No full textInternational audienceBackground/Objective: Obesity is a devastating worldwide metabolic disease, with the highest prevalence in children and adolescents. Obesity impacts neuronal function but the fate of functional hyperemia, a vital mechanism making possible cerebral blood supply to active brain areas, is unknown in organisms fed a high-caloric Western Diet (WD) since adolescence.Subjects/Methods: We mapped changes in cerebral blood volume (CBV) in the somatosensory cortex in response to whisker stimulation in adolescent, adult, and middle-aged mice fed a WD since adolescence. To this aim, we used non-invasive and high-resolution functional ultrasound imaging (fUS). Results:We efficiently mimicked the metabolic syndrome of adolescents in young mice with early weight gain, dysfunctional glucose homeostasis, and insulinemia. Functional hyperemia is compromised as early as 3 weeks of WD and remains impaired after that in adolescent mice. Starting WD in adult mice does not trigger the profound impairment in sensory-evoked CBV observed in young mice, suggesting a cerebrovascular vulnerability to WD during adolescence. In WD, ω-6:ω-3 polyunsaturated fatty acids (PUFAs) ratio is unbalanced towards proinflammatory ω-6. A balanced ω-6:ω-3 PUFAs ratio in WD achieved by docosahexaenoic acid supplementation efficiently restores glucose homeostasis and functional hyperemia in adults.Conclusions: WD triggers a rapid impairment in cerebrovascular activity in adolescence, which is maintained at older ages, and can be rescued by a PUFA-based nutraceutical approach.</div
Broadband directional thermal emission with anisothermal microsources
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Coherent combining of large-aperture high-energy Nd:glass laser amplifiers
No full textInternational audienceWe present coherent beam combining of nanosecond pulses with 20-J energy and large beams using a Sagnac interferometer geometry based on Nd:glass rod-type amplifiers. In this study, we demonstrate that coherent beam combining is compatible with large-diameter energetic beams, presenting, therefore, an interesting and solid perspective towards the performance improvement of large-scale laser facilities, especially in terms of high-repetition-rate and high-energy operation. We demonstrate that for energy of 20 J, the coherent combination efficiency is around 92%, with high beam quality and long-term stability. A thorough temporal and spatial characterization of the system’s operation is provided to forecast the various potentialities available for large-scale facilities
Quantum Nanoscopy and Optical Control: From Single Molecules to Entangled Pairs
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Développement d'un procédé de fabrication additive par voie laser pour les matériaux magnétiques : application au grenat de fer et d'yttrium
No full textThis thesis deals with the additive manufacturing of iron yttrium garnet(YIG) using selective laser melting (SLM). The study was carried out along 4 axes :1) study of process parameters to obtain ferrite samples with satisfactory consistency,2) assessment of the impact of parameters on material properties, 3) laser melting of YIGfor radio frequency and microwave applications, 4) exploration of possible developmentsto optimize the process and broaden its applications. Preliminary results showed that ananosecond laser at 1064 nm could produce YIG samples with acceptable strength. Howe-ver, further analysis revealed partial degradation of YIG into unwanted secondary phases(YIP, magnetite and wustite). The maximum achievable density was 90 %. Annealingfollowed by quenching enabled the YIG to be recombined (98%). In addition, toroidalinductors were used to assess the initial magnetic permeability, which was increased fromμr = 3.5 to μr = 45 with the heat treatment. Next, passive components for microwaveapplications were also fabricated, showing a non-reciprocal effect due to the gyromagneticresonance of ferrite (1 dB for the coplanar isolator, 12 dB for the waveguide isolator). Si-mulations suggested the use of a spatial light modulator to improve temperature controlof the melting pool. Although laser annealing tests were not sucessful, other laser para-meters could offer better prospects. The study also demonstrated the value of pulse lasersfor machining both copper and YIG, enabling hybrid monolaser manufacturing. Finally,it was possible to print ferrites on various materials such as aluminum, alumina and glass,opening up prospects for applications in fields other than radiofrequency and microwaves.Cette thèse porte sur la fabrication additive du grenat de fer et d’yttrium (YIG), par fusion sélective par laser (SLM). L’étude s’est déroulée selon 4 axes : 1) étude des paramètres du procédé pour obtenir des échantillons de ferrite avec une consistance satisfaisante, 2) évaluation de l’impact des paramètres sur les propriétés du matériau, 3) fusion laser du YIG pour les applications en radiofréquences et hyperfréquences, 4) exploration des évolutions possibles pour optimiser le procédé et élargir ses applications. Les résultats préliminaires ont montré qu’un laser nanoseconde à 1064 nm permettait de fabriquer des échantillons de YIG avec une solidité acceptable. Cependant, des analyses plus poussées ont révélé une dégradation partielle du YIG en phases secondaires non désirées (YIP, ma-gnétite et wustite). La densité maximale atteignable était de 90 %. Un recuit suivi d’une trempe a permis de recombiner le YIG (98 %). Parallèlement, des inductances toriques ont permis d’évaluer la perméabilité magnétique initiale, qui est passée de μr = 3,5 à μr =45 grâce au traitement thermique. Ensuite, des composants passifs pour les applications hyperfréquences ont également été fabriqués, montrant un effet non réciproque dû à la résonance gyromagnétique du ferrite (1 dB pour l’isolateur coplanaire, 12 dB pour l’isola-teur à guide d’onde). Les simulations ont suggéré l’utilisation d’un modulateur spatial de faisceau pour améliorer le contrôle de la température du bain de fusion. Bien que les essais de recuit laser n’aient pas été concluants, d’autres paramètres laser pourraient offrir de meilleures perspectives. L’étude a également montré l’intérêt du laser à impulsions pour usiner à la fois du cuivre et du YIG, permettant une fabrication hybride monolaser. Enfin,l’impression de ferrites sur divers matériaux comme l’aluminium, l’alumine et le verre a été possible, ouvrant des perspectives d’applications dans des domaines autres que les radiofréquences et hyperfréquences
Dosimétrie par fibre optique et instrumentation de faisceau
No full textThis thesis includes the results obtained during my PhD as part of the RADNEXT project, inside the Work Package dedicated to dosimetry and beam instrumentation. To this end, the objective of this thesis is to leverage the expertise of the MOPERE team at Laboratoire Hubert Curien in Saint Etienne, France, on the effects of ionizing radiation on optical fibers, to develop and validate new solutions for radiation detectors and dosimeters based on this technology that can help the facilities involved in the project to better answer the users’ needs in the control of the flux and fluence impinging on their devices under test.In the first chapter are listed the types of particles of interest for different radiation-rich environments, together with an explanation on their interaction with matter and how they can be generated, either via radioactive isotopes, or the many evolutions of particle accelerators. The chapter continues with a run-down of the state-of-the-art dosimeters in use today. The first chapter ends presenting the facilities that were exploited during these three years to obtain the results discussed in this thesis. The second chapter is focused on the promise of optical fibers for dosimetry. This chapter starts by laying out their promise for sensing applications and their advantages compared to electronic-based technologies.The basic concepts of silica-based optical fibers are then explained, including the mechanisms and structures required to transport light within them. The main radiation-induced effects interesting for dosimetry are introduced: radiation-induced attenuation (RIA), at the base of cumulative dose (fluence) dosimeters, and radiation-induced luminescence (RIL), used for flux (dose rate) dosimeters. The interrogator setups needed to measure these effects are presented, and their characteristics are listed to explain how different types of dosimeter can be obtained.The third chapter includes two investigations on the capability of three candidate optical fibers to act as the active element of RIA-based dosimeters. The first is a method to investigate whether a certain fiber is adapted for such a role through extensive X-ray testing while varying the irradiation conditions, in terms of both temperature and dose rate. The method is then validated on two multimode optical fibers, one with a P-doped core and one with a GeP-codoped core. The second part of the chapter investigates the peculiar RIA response of a new generation of ultra-low loss pure-silica core optical fiber. Its characteristics are investigated to explore the possibility of a reusable radiation detector. Leveraging the previous studies of the MOPERE group, this work investigates the effect that a pre-irradiation treatment at different dose values can have on the RIA of this fiber. The last part of this chapter includes a study on the compatibility of this ULL optical fiber with a distributed sensing solution working in the infrared domain.The fourth chapter presents the results from two irradiation campaigns performed in the framework of the RADNEXT project to investigate the compatibility of state-of-the-art fiber-based dosimeters in two irradiation facilities within the consortium. The first campaign was performed at ENEA’s Frascati Neutron Generator, in Frascati (Italy). Here, we used the 14 MeV neutron generator to irradiate Ce-doped radioluminescent optical fibers and demonstrate their capability to monitor in real-time the neutron flux. The second campaign had the goal to explore the compatibility between fiber-based dosimeters, both RIA and RIL-based, and a new type of particle accelerator based on PW laser-matter interaction at the Centro de Láseres Pulsados (CLPU) of Salamanca, Spain. The investigation aims to fill a gap in the selection of dosimeters capable of measuring laser-generated protons, as the harsh electromagnetic environment generated with the interaction impedes the use of the most common electronic-based sensors.Cette thèse présente les résultats obtenus durant mon doctorat dans le cadre du projet RADNEXT, au sein du lot de travail dédié à la dosimétrie et à l'instrumentation des faisceaux. L'objectif de ce travail est de s'appuyer sur l'expertise de l'équipe MOPERE du Laboratoire Hubert Curien à Saint-Étienne, France, concernant les effets des rayonnements ionisants sur les fibres optiques, afin de développer et valider de nouvelles solutions de détecteurs de rayonnements et de dosimètres basés sur cette technologie. Ces solutions visent à aider les installations de tests du projet à mieux répondre aux besoins des utilisateurs dans le contrôle du flux et de la fluence sur leurs dispositifs en cours de test.Le premier chapitre décrit les types de particules d'intérêt dans différents environnements riches en radiations, en expliquant leurs interactions avec la matière et leurs modes de production, qu'ils proviennent d'isotopes radioactifs ou d'accélérateurs de particules. Il passe ensuite en revue l'état de l'art des dosimètres actuels et présente les installations d'irradiation utilisées pour obtenir les résultats discutés dans cette thèse.Le deuxième chapitre est consacré au potentiel des fibres optiques pour la dosimétrie. Après avoir présenté leurs avantages pour les applications de détection par rapport aux technologies électroniques, les concepts fondamentaux des fibres optiques en silice sont expliqués, notamment les mécanismes de transport de la lumière. Les principaux effets induits par les radiations sont abordés : l'atténuation induite par l'iradiation (RIA), base des dosimètres pour la fluence, et la luminescence induite par les radiations (RIL), utilisée pour la mesure du flux. Les dispositifs de lecture permettant de mesurer ces effets sont présentés et leurs caractéristiques sont détaillées pour illustrer les différentes configurations de dosimètres possibles.Le troisième chapitre décrit deux études sur la capacité de trois fibres optiques candidates à fonctionner comme éléments actifs de dosimètres basés sur la RIA. La première étude propose une méthode pour évaluer l'adaptabilité d'une fibre à ce rôle via des tests aux rayons X, en faisant varier la température et le débit de dose. Cette méthode est validée sur deux fibres multimodes : l'une avec un coeur dopé au phosphore (P) et l'autre co-dopée au germanium et au phosphore (GeP). La seconde étude explore la réponse RIA d'une fibre à coeur en silice pure à ultra-faible perte (ULL) en vue de développer un détecteur réutilisable. L'effet d'un pré-traitement d'irradiation sur cette fibre est analysé, et sa compatibilité avec une solution de détection répartie dans le domaine infrarouge est évaluée.Le quatrième chapitre présente les résultats de deux campagnes d'irradiation menées dans le cadre de RADNEXT pour évaluer la compatibilité des dosimètres à fibres optiques dans deux installations du consortium. La première campagne, réalisée au générateur de neutrons de 14 MeV de l'ENEA à Frascati (Italie), a permis de démontrer la capacité des fibres radioluminescentes dopées au cérium à mesurer en temps réel le flux de neutrons. La seconde campagne, menée au Centro de Láseres Pulsados (CLPU) de Salamanque (Espagne), explore la compatibilité des dosimètres basés sur la RIA et la RIL avec un accélérateur de particules innovant fonctionnant par interaction laser-matière à haute puissance. Cette étude vise à combler un manque de solutions de dosimétrie adaptées aux protons générés par laser, les conditions électromagnétiques extrêmes interdisant l'usage des capteurs électroniques classiques
Symbolic Monte Carlo for Quantifying Fluorescent Biomarkers in Neurosurgical Intraoperative Imaging
No full textInternational audienceSymbolic Monte Carlo methods are employed to quantify the fluorescent biomarker Protoporphyrin IX, utilized in neuro-oncology. The outcome matches the experimental measurements setting SMC simulations as a promising tool for intraoperative imaging neurosurgery