HAL Portal IOGS (nstitut d'Optique Graduate School)
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Quasicrystalline approximation for predicting the structural colors of disordered plasmonic metasurfaces
No full textInternational audienc
Unsupervised spatiotemporal classification of deformation patterns of embryonic tissues matches their fate map
No full textInternational audienceDuring morphogenesis, embryonic tissues display fluid-like behavior with fluctuating strain rates. Digital cell lineages reconstructed from 4D images of developing zebrafish embryos are used to infer representative tissue deformation patterns and their association with developmental events. Finite deformation analysis along cell trajectories and unsupervised machine learning are applied to obtain reduced-order models condensing the collective cell motions, delineating tissue domains with distinct 4D biomechanical behavior. This reduced-order kinematic description is reproducible across specimens and matches fate maps of the zebrafish brain in wild-type and nodal pathway mutants (zoeptz57/tz57), shedding light into the morphogenetic defects causing these mutants’ cyclopia. Furthermore, the inferred kinematic maps also match expression maps of the gene transcription factor goosecoid (gsc). In summary, this work introduces an objective analytical framework to systematically unravel the complex spatiotemporal patterns of embryonic tissue deformations and couple them with cell fate and gene expression maps
Photonic neuromorphic computing using symmetry-protected zero modes in coupled nanolaser arrays
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Exploring the relationship between humans and lighting beyond physics: the case of traditional Japanese interior lighting
No full textInternational audienceThe complex and deep relationships that people have had with lighting throughout the ages in various parts of the world are difficult to grasp from a scientific point of view due to an incredible intertwining of physical, technological, physiological, psychological, sociological, aesthetic, cultural, historical, and geographical factors, as well as the difficulty of accessing accurate sources of information. However, studying this relationship between humans and light in all its dimensions is fruitful at a time when lighting technologies and the design of urban environments are undergoing major changes. This study attempts to initiate a transdisciplinary reflection on these issues through the example of interior lighting in traditional Japanese housing before the advent of electric lighting, supported by scientific contributions from multiple disciplines and the literary testimony of Junichirō Tanizaki in In Praise of Shadows
Capteur inertiel compact à atomes froids piégés sur puce
No full textThe work presented in this manuscript focuses on the development of an inertial sensor based on cold atoms trapped on an atom chip for inertial navigation. Based on the principles of atom interferometry, these devices exploit the quantum properties of cold atoms to accurately measure accelerations and rotations. The experimental complexity and bulk of these laboratory experiments pose major obstacles for some embedded applications. In the late 1990s, the possibility of trapping and manipulating atoms on atom chips was demonstrated, enabling a significant reduction in the size of cold atom sensors as well as their power consumption. This thesis is part of an effort to miniaturize and optimize quantum sensors, aiming to demonstrate the feasibility of a compact architecture.Our inertial sensor is based on a Ramsey sequence with a spatial splitting of internal states, making the interferometer sensitive to accelerations. In particular, we demonstrate a noise level of 3 mg at one shot on the acceleration measurement, and an in-depth study of the accelerometer's noise budget is also being conducted.In addition to reducing the size of the sensor itself with an atom chip, work is being done on miniaturizing the optical system required to prepare the laser beams for the experiment. In collaboration with Exail, we have designed a miniature optical bench with a volume of 4.4 L for cooling atoms in a 3D magneto-optical trap and promises to further reduce the size of cold atom sensors for embedded applications.Le travail présenté dans ce manuscrit porte sur le développement d'un capteur inertiel basé sur des atomes froids piégés sur une puce atomique pour la navigation inertielle. Basés sur les principes de l'interférométrie atomique, ces dispositifs exploitent les propriétés quantiques des atomes froids pour mesurer avec précision les accélérations et les rotations. La complexité expérimentale et l'encombrement de ces expériences de laboratoire constituent des obstacles majeurs pour certaines applications embarquées. A la fin des années 1990, il a été démontré la possibilité de piéger et manipuler des atomes sur des puces atomiques, rendant possible une réduction significative de la taille des capteurs à atomes froids ainsi que de leur consommation énergétique. Ces travaux de thèse s'inscrivent dans un effort de miniaturisation et d'optimisation des capteurs quantiques, visant à démontrer la faisabilité d'une architecture compacte.Notre capteur inertiel est basé sur une séquence de Ramsey avec une séparation spatiale des états internes, rendant l'interféromètre sensible aux accélérations.Nous démontrons en particulier un bruit sur la mesure d'accélération de 3 mg par coup et une étude approfondie du budget de bruit de l'accéléromètre est également réalisée.En plus de la réduction de la taille du capteur lui-même avec une puce atomique, un travail est effectué sur la miniaturisation du système optique nécessaire à la préparation des faisceaux laser de l'expérience. En collaboration avec Exail, nous avons conçu un banc optique miniature d'un volume de 4,4 L permettant de refroidir les atomes dans un piège magnéto-optique 3D et promet de réduire davantage la taille des capteurs à atomes froids pour des applications embarquées
Déploiement d'une approche par compétences : comment transformer de façon collégiale ?
No full textInternational audienceIn this paper, the project team, made up of teachers and teacher-researchers from the school, and educational science researchers, describe the method used to construct a competency referential on a collegial basis, and the beginnings of its deployment in a French engineering school. The focus is on the interaction modalities implemented for the various members of the training ecosystem: the project team, teaching teams, students, professional and academic partners, and educational science experts. The various methods used have led to the creation of a competency referencial and operationnal evaluation grids for competency levels, which are currently being rolled out across the entire curriculum.Dans cette communication, la méthode de construction collégiale d'un référentiel de compétences ainsi que l'amorce de son déploiement dans une école d'ingénieur française sont décrits par l'équipe-projet, formée par des enseignant•es et enseignant•es-chercheur•es de l'école, et des chercheurs en sciences de l'éducation. Le propos est centré sur les modalités d'interactions mises en oeuvre à l'attention des différents membres de l'écosystème de formation : l'équipe-projet, les équipes enseignantes, les étudiant•es, les partenaires professionnels et académiques, les expert•es en sciences de l'éducation. Les modalités variées mises en place ont permis de disposer d'un référentiel de compétences et des grilles d'évaluation des niveaux de compétences opérationnelles, en cours de déploiement sur l'ensemble de la formation
Fourier Finite-Difference method and Proper Orthogonal Decomposition for quick spectral study of 2D periodic photonic structures
No full textWe present an original electromagnetic solver for three-dimensional photonic structures with a two-dimensional periodicity. It is based on Fourier expansions in the two periodic directions and an elegant yet efficient combination of finite-difference discretization and modal treatment in the propagation direction. The Fourier Finite Difference Method (FFDM) is cast into an easy-to-handle, agile, and efficient matrix formalism. Our approach uses matrix inversions instead of eigenmodes computations, a strategy that confers a clear advantage in terms of computation time for the large Fourier truncation orders that are typically used to deal with micro and nanophotonic structures of current interest. Therefore, it is particularly well suited for the analysis of generalized grating structures and metasurfaces. The computational gain increases with the Fourier truncation order. It is maximal (10-30) for coarse finite-difference steps, which are nevertheless sufficient to achieve a relative accuracy of approximately 1%. A second important advantage of the proposed method is the possibility of using model-order reduction techniques. We use Proper Orthogonal Decomposition (POD), in conjunction with the snapshot technique, to further speed up the computation of diffraction spectra as a function of the frequency, the incident angle, or any geometric parameter
Extending the Range of Sizes of Monodisperse Core‐Shell Hydrogel Capsules from Composite Jet Breakup by Combined Electrical and Mechanical Actuation
No full textInternational audienceThe production of monodisperse particles or droplets is a longstanding issue across various fields, from aerosol science to inkjet printing. In bioengineering, sub‐millimeter cell‐laden hydrogel capsules have proven valuable for developing in vitro tissue models. A common practical approach for producing such droplets relies on the Plateau–Rayleigh instability to break up a liquid compound jet in air. However, while the droplet size is closely linked to nozzle dimensions, achieving high monodispersity suitable for quantitative biological assays remains challenging due to coalescence events associated with the beads‐on‐a‐string morphology of viscoelastic jets. Here, a microfluidic strategy is introduced, combining electrical and mechanical actuation to enhance control and versatility over jet breakup. By fine‐tuning the excitation frequency to select specific modes and applying an electric potential to regulate coalescence, a phase diagram is established, enabling the generation of monodisperse droplets over a broad size range. Notably, a previously hidden effect of the electric field on jet behavior is uncovered and quantitatively characterized. Finally, after crosslinking the compound droplets, capsules with a hydrogel envelope and a core composed of a cell suspension are formed in conditions compatible with cell proliferation, which lay the groundwork for quantitative high precision biological assays
Potential of radioluminescent silica-based optical fibers for 14 MeV neutron beam monitoring
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LED pumped alexandrite multipass amplifier designed for acousto-optic imaging
No full textInternational audienceIn this paper we present an alexandrite (Cr 3+ :BeAl 2 O 4 ) multipass amplifier pumped by blue LEDs via a luminescent concentrator (LC). This emerging pump technology provides up to 2.6 kW optical pump power during 400 µs at 10 Hz in the 530-630 nm range for low cost, simple and robust implementation. We achieve a single-pass gain of 1.38, the highest ever reported in alexandrite for a semiconductor-based pump source, and a total gain of 34 after 16 passes. The amplifier is injected by a single-frequency laser operating in a quasi-continuous wave at 761 nm. It delivers µs pulses with a peak power of 14 W. This power could significantly improve penetration depth for in vivo acousto-optic imaging