HAL Portal IOGS (nstitut d'Optique Graduate School)
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Micro-nanostructuration par lithographie par nano-impression (NIL) de films élaborés par voie sol-gel pour la génération photocatalytique de carburants solaires
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Multiphoton Atom Interferometry via Cavity-Enhanced Bragg Diffraction
No full textInternational audienceWe present a novel atom interferometer configuration that combines large momentum transfer with the enhancement of an optical resonator for the purpose of measuring gravitational strain in the horizontal directions. Using Bragg diffraction and taking advantage of the optical gain provided by the resonator, we achieve momentum transfer up to 8ℏk with mW level optical power in a cm-sized resonating waist. Importantly, our experiment uses an original resonator design that allows for a large resonating beam waist and eliminates the need to trap atoms in cavity modes. We demonstrate inertial sensitivity in the horizontal direction by measuring the change in tilt of our resonator. This result paves the way for future hybrid atom or optical gravitational wave detectors. Furthermore, the versatility of our method extends to a wide range of measurement geometries and atomic sources, opening up new avenues for the realization of highly sensitive inertial atom sensors
TSC-1 Offner Spectrometer Prototype Characterization
No full textInternational audienceThe Thai Space Consortium (TSC) has undertaken the development of an Offner spectrometer prototype for the TSC-1 satellite mission, aiming to enhance Earth observation capabilities. Through systematic parameter selection and radiometric analyses, optimal performance of the hyperspectral imager within established specifications was achieved in the previous study. The design phase involved selecting a two-mirror off-axis telescope coupled with the Offner spectrometer for its diffraction-limited performance. Rigorous testing validated the prototype’s alignment with simulated performance, affirming its ability to meet demanding Earth observation requirements. The experimental results demonstrate that the Offner spectrometer prototype has been successfully developed. The spatial resolution ranges between 21.0 and 24.1 µm, and the spectral resolution ranges between 7.3 and 8.7 nm, with no significant distortion. Furthermore, the signal-to-noise ratio at 550 nm is 100. This achievement positions the TSC at the forefront of innovative Earth observation instrumentation in Thailand, with implications for future space missions requiring precise and efficient hyperspectral imaging
Nouveaux résultats analytiques sur le décalage latéral dû à la réfraction atmosphérique
No full textOur two analytical methods of studying the total lateral shift Δoo related to astronomical refraction, described in our article [1], are carrying new and unprecedented results, which we presented at the seminar that we gave at ONERA (Palaiseau), 12-16-2024. On the one hand, the detailed exploitation of the Bouguer invariant allows us to show, with numerical values in support, how to give a development of Δoo, within the astronomical horizon, at order 2 (relative to the apparent height) in relation to the asymmetry of the image of the setting sun and diagnose non-standard cases of it that go visually unnoticed. On the other hand, the exploitation of the quadrature governing the light rays in a continuous medium with spherical symmetry allows us to develop Δoo according to the air refractivity, not only at order 1 as in [1], but at order 2 (which allows to better highlight the questions of mathematical methodology), and thus obtain a new approximate expression of Δoo, more efficient. We show that it accounts very well numerically (up to and including the zenith distance of 75°) for non-linearity of Δoo as a function of pressure, as shown by [2] but left unexplained; we take advantage of this to predict the effects, on previous results, of the violation of the Gladstone-Dale rule (paradoxically more important than those of the violation of the ideal gases law); we also analyze the small variation (null, according to Rayleigh) of Δoo with temperature, and show that there is an unexplained residue which remains mysterious because it is probably not due to order 3. We also obtain an original integral formula, and its series expansion, for the lateral shift due to the propagation through a supposedly stratified atmosphere. Finally, we study quantitatively the effect, on Δoo, of the presence of an inversion layer above the observer, and recall (through a historical model) that it can cause critical phenomena to appear which may exalt chromatic dispersion for Δoo, compared to its standard dispersion on the astronomical horizon.Nos deux méthodes d’étude analytique du décalage latéral total Δoo lié à la réfraction astronomique, exposées dans notre article [1], sont porteuses de nouveaux résultats inédits, que nous avons présentés à l’occasion du séminaire que nous avons donné à l’ONERA (Palaiseau) le 16 / 12 / 2024. D’une part, l’exploitation approfondie de l’invariant de BOUGUER nous permet de montrer, valeurs numériques à l’appui, comment donner un développement de Δoo au voisinage de l’horizon astronomique à l’ordre 2 (par rapport à la hauteur apparente) en lien avec l’asymétrie de l’image du Soleil couchant – et diagnostiquer des cas non-standard de celle-ci qui passent visuellement inaperçus. D’autre part, l’exploitation de la quadrature régissant les rayons lumineux dans un milieu continu à symétrie sphérique nous permet de développer Δoo en fonction de la réfractivité, non seulement à l’ordre 1 comme dans [1], mais à l’ordre 2 (ce qui permet de mieux mettre en évidence les questions de méthodologie mathématique), et d’obtenir ainsi une nouvelle expression approchée de Δoo, plus performante. Nous montrons qu’elle rend très bien compte numériquement (jusqu’à la distance zénithale 75° inclus) de la non-linéarité de Δoo en fonction de la pression, mise en évidence par [2] mais laissée inexpliquée ; nous en profitons pour prédire les effets, sur les résultats précédents, de la violation de la loi de GLADSTONE-DALE (paradoxalement plus importants que ceux de la violation de la loi des gaz parfaits) ; nous analysons aussi la petite variation (nulle selon RAYLEIGH) de Δoo avec la température, et montrons qu’il subsiste un résidu inexpliqué qui reste mystérieux car il n’est vraisemblablement pas dû à l’ordre 3. Nous obtenons aussi une formule intégrale inédite, et son développement en série, pour le décalage latéral à la traversée d’une atmosphère supposée stratifiée. Enfin, nous étudions quantitativement l’effet, sur Δoo, de la présence d’une couche d’inversion au-dessus de l’observateur, et rappelons (grâce à un modèle historique) qu’elle peut faire apparaître des phénomènes critiques susceptibles d’exalter la dispersion chromatique pour Δoo, par rapport à sa dispersion standard sur l’horizon astronomique
Plasmonic hydrogen sensor at the ppm level based on the plasmon-triggered switching
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Beyond Total Locking: Demonstrating and Measuring Mutual Influence on a RO-Based True Random Number Generator on an FPGA
No full textInternational audienceRing oscillator-based true random number generators are of interest because of their well-known and well-characterised conversion of analog noise into random numbers. The main drawback of using ring oscillators as a source of randomness is their tendency to be influenced by their environment. In particular, oscillators may lock to another signal at a frequency close to the nominal frequency of the ring, or two or more rings may even lock to each other. This is particularly dangerous for generators with multiple rings, which require the rings to be independent of each other. Furthermore, to reduce the risk of manipulable global noise sources, the rings should have the same structure and topology, making them even more vulnerable to locking. The metrics commonly used to quantify the degree of locking have limitations that can lead to erroneous conclusions as to whether a ring is locked or not. This is why we prefer to use the term mutual influence. In this paper, we propose a clear definition of the mutual influence between ring oscillators used as sources of randomness. One of the advantages of this definition is that it can easily be extended to include the case of the total locking of rings. Based on this definition, we introduce a new metric to quantify the mutual influence, which evaluates a statistical distance between the current distribution of phase differences and uniform distribution. The experimental results of several FPGA implementations of ring oscillators highlighted the suitability of the Kolmogorov-Smirnov test as a metric for detecting mutual influence
Probing non-Hermitian zero modes in a nanophotonic trimer: From nonuniform to twisted coupling
No full textInternational audienceAbstract Recent studies on exceptional points (EPs) in non-Hermitian optical systems have revealed unique traits, including unidirectional invisibility, chiral mode switching and laser self-termination. In systems featuring gain/loss components, EPs are commonly accessed below the lasing threshold, i.e., in the linear regime. In this work, we experimentally demonstrate that EP singularities in coupled semiconductor nanolasers can be accessed above the lasing threshold, where they become branch points of a nonlinear dynamical system. Contrary to the common belief that unavoidable cavity detuning impedes the formation of EPs, here we demonstrate that such detuning is necessary for compensating the carrier-induced frequency shift, hence restoring the EP. Furthermore, we find that the pump imbalance at lasing EPs varies with the total pump power, enabling their continuous tracking. This work uncovers the unstable nature of EPs above laser threshold in coupled semiconductor lasers, offering promising opportunities for the realization of self-pulsing nanolaser devices and frequency combs
Forming 1D Periodic J-aggregates by Mechanical Bending of BNNTs: Evidence of Activated Molecular Diffusion
No full textSupplementary added page 21Driving molecular assembly into micrometer-scale patterns is key for defining advanced materials of interest in various fields, including life sciences, photovoltaics, and quantum photonics. However, the driving process competes with other forces, such as Brownian motion, ripening phenomena, capillary forces, and non-specific adsorption. Here we report on a guided diffusion mechanism of luminescent dye molecules encapsulated inside boron nitride nanotubes (BNNTs). Correlative measurements between BNNT bending and molecular position along the BNNT axis reveal an efficient and long-range migration of dyes from curved to straight regions of the nanotube. This curvature activated diffusion forms clusters of bright J-aggregates in periodic patterns of well-defined spacing and length. A phenomenological model of guided molecular transport in bended BNNTs is used to describe this directed 1D diffusion inside BNNT. It is shown to accurately predict the position and morphologies of a J-aggregate as a function of nanotube length. Coupling topological stimuli to 1D molecular diffusion at the nanoscale is here presented as an interesting tool capable of reconfiguring various emissive patterns of functional molecules at the mesoscopic scale
Détection d'atomes uniques dans des réseaux optiques par microscopie de fluorescence
No full textInternational audienceNous présentons un nouvel algorithme permettant de détecter des atomes uniques dans des réseaux optiques à partir d’images obtenues par microscopie de fluorescence. Notre méthode offre d’excellents résultats pour des temps de calcul réduits, même lorsque le pouvoir de résolution optique est bien inférieur à la distance entre atomes