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International audience; The Saint-Maurice residence in Cairo fully illustrates the reuse of Islamic architectural elements during the 19th century. Built between 1875-1879, it was dismantled in 1937. The decorative elements are certainly those of the current French Embassy in Cairo. If the multiform documentation is large, the information on the building remains incomplete. Our work toward a 3D restitution tends to demonstrate that these technologies are particularly suitable for understanding and validating multiple and fragmentary data for architectural studies. For this purpose, photographic and 3D data were acquired on-site (including ceilings and doors at the French Embassy) and compared with surveys or even old photographs and lithographs. 3D modeling based on these elements leads to a renewed visualization of the volumes, as well as the outbreak of architectural and structural inconsistencies (plans of an older state) which made it possible to refine the restitution hypotheses. The confrontation of documents with a 3D restitution has provided some answers. The acquired ceiling of the "grand salon", when placed back in the 3D model, demonstrates that the current dimensions are similar to the original ones. The other dimensions of the building are now more validated by adjustments as close as possible to all the documents. This leads to discard certain plans which appear to be architectural preliminary blueprints prior to the residence built. Enriched by hyperspectral images, this work has shown a posteriori that the origins of architectural ornaments, particularly ceramics, may be more diversified than expected. This research constitutes an essential milestone in a better understanding of the Islamic reuses of this building. However, remains to better characterize the origin of the ceramics and the appearance of the painted and sculpted decorations of the Saint-Maurice Residence in order to be able to compare it with the existing visual documents.

International audience; The breakdown voltage (Vb) of gases can be reasonably estimated using Paschen's law, which is based on assumptions such as a perfectly uniform electric field, and infinite electrode size. This analytical approach has demonstrated remarkable capability in redicting Vb in numerous cases, by scaling it by the product of pressure and nter-electrode distance (p·d). This description is quite efficient and convenient over wide ranges of pressure and gap distance. However, the robustness of Paschen's law in predicting consistent values of Vb is severely compromised at gap distances shorter than typically 1 micrometer at atmospheric pressure. Several studies have provided experimental, theoretical, and simulation evidences highlighting these limitations. This raised significant concerns, both theoretical and practical, about the insulation properties of gases at short distances. This study focuses on experimentally investigating Vb of air in short electrode gaps, ranging from 100 nm to 6 μm. The electrode system consists of a silicon wafer coated with gold, connected to ground. The anode connected to high voltage is a sharp CuBe needle coated with gold, with 20 μm tip radius of curvature. The gap distance is controlled by a piezoelectric actuator. Ambient air is used at atmospheric pressure, allowing for comparisons with data from existing literature. Complementary experiments are also performed in a closed chamber allowing to vary the pressure from 10-4 mbar to 3.0 bar, and control the gas purity and water content.

International audience; We report the experimental generation of a broadband and flat mid-infrared supercontinuum in a silicongermanium-on-silicon two-stage waveguide. Our particular design combines a short and narrow waveguide section for efficient supercontinuum generation, and an inverse tapered section that promotes the generation of two spectrally shifted dispersive waves along the propagation direction, leading to an overall broader and flatter supercontinuum. The experimentally generated supercontinuum extended from 2.4 to 5.5 µm, only limited by the long wavelength detection limit of our spectrum analyzer. Numerical simulations predict that the supercontinuum actually extends to 7.8 µm. We exploit the enhanced flatness of our supercontinuum for a proof-of-principle demonstration of free-space multi-species gas spectroscopy of water vapor and carbon dioxide.

International audience; Codoped (Tb,Eu) ZnO films grown by magnetron sputtering on a silicon substrate and annealed up to 1200 °C showed intense photoluminescence (PL) emission from Eu3+ ions. The high-temperature annealing led to diffusion and segregation of rare earth (RE) elements toward the bottom of the film, which induced the formation of nanometric Zn-free inclusions responsible for remarkable PL emission intensity. Combined electron diffraction, chemical contrast imaging, and optical studies of these nanometric phases have been carried out. Large inclusions of zinc silicates and RE silicates a few hundreds of nanometers in size were observed, embedded in a silica phase. The structural determination of these RE-rich inclusions was carried out by combining atomic Z contrast imaging (high-angle annular dark-field imaging) and precession electron diffraction data. Upon annealing at 1200 °C, it appeared that the structure was related to an F-type disilicate structure. Energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy experiments were carried out to determine the ratios between elements and the oxidation states of the RE elements in the abovementioned inclusions. A (Tb,Eu)2Si2O7 formulation is proposed from dynamical precession electron diffraction tomography refinements, leading to a +III valence state for the RE species in agreement with spectroscopic results. PL modeling is also in good agreement with the experimental data. These results complete those obtained at 1100 °C for which the inclusions were identified as some RE10–x(SiO4)6O2–x oxyapatite structures and pointed out a combined structural and PL properties’ evolution between 1100 and 1200 °C annealing temperatures.

International audience; The photoluminescence (PL) of monolayer tungsten disulfide (WS2) is locally and electrically controlled using the nonplasmonic tip and tunneling current of a scanning tunneling microscope (STM). The spatial and spectral distribution of the emitted light is determined using an optical microscope. When the STM tip is engaged, short-range PL quenching due to near-field electromagnetic effects is present, independent of the sign and value of the bias voltage applied to the tip–sample tunneling junction. In addition, a bias-voltage-dependent long-range PL quenching is measured when the sample is positively biased. We explain these observations by considering the native n-doping of monolayer WS2 and the charge carrier density gradients induced by electron tunneling in micrometer-scale areas around the tip position. The combination of wide-field PL microscopy and charge carrier injection using an STM opens up new ways to explore the interplay between excitons and charge carriers in two-dimensional semiconductors.

Architectural glazing has several advantages in terms of aesthetics and user well-being perspectives. However, they can have large impacts on heating and cooling demands and artificial lighting requirements. Ethylene tetrafluoroethylene (ETFE) cushion systems present adequate insulating and transparency characteristics, and, combined with organic photovoltaic (OPV) modules, become a glazing element leading towards energy efficient buildings. The present manuscript reports on a detailed optical, thermal and electrical analysis of a 3-layer ETFE/ OPV cushion that helps the design of these glazing-type systems by providing a better understanding of their performance. Spectrophotometric optical measurements up to 50 µm allow proper estimations of an individual layer radiative behavior. As a matter of fact, these measurements feed the radiative and thermal models that aim at determining the behavior of the organic photovoltaic module as a function of its position in the cushion. Based on the organic photovoltaic module spectral response, electrical power production is estimated. Results reveal that the best configuration is the one placing the organic photovoltaic module in the outer layer, since it represents the case where the OPV module performs better due to the higher incident irradiance and the low dependency on temperature of the generated power. This research was supported by the ‘‘Generalitat de Catalunya’’, Spain (2017 SGR 1276 and ICREA Academia) and ‘‘Ministerio de Ciencia e Innovación’’ of Spain (grant reference PID2019- 111536RB-I00/AEI/10.13039/501100011033). The authors would like to acknowledge the collaboration with the company IASO SA.

International audience; True north can be determined on Earth by three means: magnetic compasses, stars, and via the global navigation satellite systems (GNSS), each of which has its own drawbacks. GNSS are sensitive to jamming and spoofing, magnetic compasses are vulnerable to magnetic interferences, and the stars can be used only at night with a clear sky. As an alternative to these methods, nature-inspired navigational cues are of particular interest. Celestial polarization, which is used by insects such as Cataglyphis ants, can provide useful directional cues. Migrating birds calibrate their magnetic compasses by observing the celestial rotation at night. By combining these cues, we have developed a bioinspired optical method for finding the celestial pole during the daytime. This method, which we have named SkyPole, is based on the rotation of the skylight polarization pattern. A polarimetric camera was used to measure the degree of skylight polarization rotating with the Sun. Image difference processes were then applied to the time-varying measurements in order to determine the north celestial pole’s position and thus the observer’s latitude and bearing with respect to the true north.

International audience; The understanding and analyzing of solid particle behavior in a liquid is a challenge in numerouse fields and engineering industry as the petroleum or the cosmetic one. It is indeed essential to know the behavior of soft matter process to avoid problems and ensures the product quality. This study presents the viscosimeter development working on a resonant optical signal principle by measuring the Free Spectral Range (FSR) parameter of a resonant optical mode during nanoparticles (NPs) sedimentation in a liquid which consists of a water/glycerol mixture. The photonic structure is composed of racetracks micro-resonators made of a UV210 polymer fabricated by deep-UV photolitography developped on an oxydated silicon layer to get a Si/SiO 2 bi-layer. The chip is then integrated in an optical bench to track the evolution of the FSR during the complet sedimentation process. The resonant signal analyse established by an adapted signal processing of silica nanoparticles sedimentation in different water/glycerol concentrations allows us to determine stages and velocity rate of the sedimentation process to finaly access to their viscosity. At the same time, measures are performed on a commercial mechanical rheometer so as to compare the dynamic evolution of their viscosity and their associated FSR. The plot of those data versus the glycerol concentration in water obviously shows a possible mathematical transformation between viscosity and FSR slope. There is therefore a good agreement between mechanical and resonant optical measures if we consider the dynamic evolution of both curves ; so this work proves the feasability of an optical viscosimeter based on resonant signal.

International audience; Integrated optics has been intensively developed the last decades for the production of components for telecommunications or sensors in metrology. The basic element constitutes the waveguide which transmits the information by guiding the light. The manufacturing processes take place in clean rooms with controlled atmosphere (pressure, temperature, dust) and with generally various deposition and coating machines. The production of these photonics devices remains relatively expensive since it is carried out in a clean room by series of manipulations which requires the intervention of a specialized engineer into a specific environment. More recently, techniques for manufacturing different mechanical parts of mostly research scientific devices have been developed using commercial 3D printers without the need of clean room environment. With such commercial machines, plastic materials are heated and then shaped by controlling their flow through a nozzle. This work concerns the study of the feasibility of realizing and shaping a kind of integrated optics by a simple 3D printer in a normal environment. It aims to understand and develop the fabrication of an integrated planar optics with polymer waveguides using a 3D printer and G-code programming. The coating processes and the G-codes of the 3D printer have been developed in order to produce the thermoplastic polyurethane (TPU) guiding structures onto a silicon/silica wafer. Finally, the characterization of this TPU organic (measurements of surface or energy tension, Raman analysis, ellipsometry measurements) and the optical injection made possible to validate this concept in terms of production and approach. The results concerning the shaping of various rib waveguides and obtaining a propagation of the light in organic thermoplastic polyurethane planar guides with fiber tapers by this simple and low-cost printing processes are positive. This work further proves that the development of integrated optics on thermoplastic polyurethane by 3D printing is possible; this opens the way to the realization of other optical patterns based on the 3D printer principle.

International audience; In this paper, a zero-crossings based method is proposed to improve the displacement sensing performance of nonuniform sampling (NUS) theory based use of optical feedback interferometry (OFI) under moderate optical feedback regime. The incorporation of zero-crossings as phase quantization levels allows doubling the samples for subsequent interpolation, without using any dithering scheme. When compared to the simple dither-free NUS method, the proposed method yields an overall improvement in RMS error over a wide range of target motion amplitudes and frequencies, with maximum improvement at low amplitudes. Experimentally, an improvement of up to 87% is obtained in precision as compared to simple NUS system for an OFI sensor with laser wavelength of 785 nm.

National audience; We present here a demonstration of THz transmission system enabling a full frequency duplex link in the 300 GHz band. This system is coupling a super-heterodyne architecture, E-band modems and duplexing system at 300 GHz.; Nous présentons ici une démonstration d'un système de transmission THz permettant une liaison fréquentielle bidirectionnelle simultanée dans la bande des 300 GHz. Ce système associe une architecture super-hétérodyne, des modems en bande E et un système de duplexage à 300 GHz.

International audience; Les oscillateurs optoélectroniques (OEO) suscitent beaucoup d’intérêt pour leur capacité à produire des signaux RF sur porteuse optique avec un très bas bruit de phase, à des fréquences pouvant aller jusqu’à quelques dizaines de GHz. Les OEO peuvent parallèlement générer des impulsions optiques de faible gigue, soit dans des architectures de type COEO, soit en tirant partie des effets combinés de la dispersion et de l’automodulation de phase dans la ligne à retard de l’OEO. Récemment, des architectures de type OEO à modulation directe ont été étudiées, démontrant des performances intéressantes tant pour la génération de signaux à bas bruit de phase que pour la génération des peignes optiques. Dans cette contribution, nous adaptons l’architecture proposée en [5] pour générer des impulsions courtes de faible gigue.

National audience; L'objectif du travail présenté ici est de développer une interface photothermique composée de nanoantennes capables d'absorber le rayonnement solaire infrarouge pour le convertir en chaleur. Cette étude s'étend de la conception des nanoantennes individuelles par simulations électromagnétiques à la réalisation expérimentale d'interfaces photothermiques nanostructurées montrant un échauffement de plus de 7°C sous le rayonnement solaire infrarouge. Cette interface a vocation à être intégrée au sein de dispositifs de cogénération photovoltaïquethermoélectrique, afin d'en augmenter l'efficacité de conversion de l'énergie solaire en électricité. Nous présentons donc ici un outil de modélisation multiphysique destiné à étudier l'impact d'une telle interface sur les performances du système photovoltaïque-thermoélectrique.

International audience; The need for low cost photovoltaic solutions is becoming more and more important with the ongoing NewSpace revolution. In this context, alternative solar cell technologies are under the spotlight, in particular perovskites which can reach high specific power. In this study, we investigate the electron and proton radiation hardness of multi-cation mixed halide perovskite cells CsxFA1-xPb(IyBr1-y)3. The proton irradiations demonstrate an excellent radiation hardness of the perovskite material but also highlight the degradation of the HTL layer. And the in-situ IV measurements under vacuum following the electron irradiations reveals a self-healing phenomena.; Le besoin de solutions photovoltaïques à faible coût devient de plus en plus important avec la révolution NewSpace en cours. Dans ce contexte, les technologies alternatives de cellules solaires sont sous les feux de la rampe, en particulier les pérovskites qui peuvent atteindre une puissance spécifique élevée. Dans cette étude, nous étudions la dureté aux rayonnements électroniques et protoniques des cellules pérovskites à halogénures mixtes multi-cations CsxFA1-xPb(IyBr1-y)3. Les irradiations aux protons démontrent une excellente résistance aux radiations du matériau pérovskite, mais mettent également en évidence la dégradation de la couche HTL. Les mesures in situ de l'IV sous vide après les irradiations aux électrons révèlent un phénomène d'auto-guérison.

International audience; In this work, we performed laser annealing of thin Sb2Te3 films to optimize crystallization time and their nonlinear optical properties. The annealed layers were studied by electron microscopy and UV–Vis spectrophotometry. Their nonlinear optical response was investigated by nonlinear transmission and Z-scan measurements. These studies were performed by a femtosecond laser system providing 400 fs laser pulses at 1030 nm. The results were compared with previous findings based on studies of oven-annealed thin films.

International audience; We put forward the use of transparent 3D displays for augmented reality. For a glasses-free experience with autostereoscopy and a large viewing area, we study the use of a recent transparent display with multiple discrete and horizontally adjacent viewing zones. Although promising, this display cannot directly be used for augmented reality due to inconsistencies within and between the discrete viewing zones. In this work, we propose to overcome this limitation by tracking the user's eyes for ensuring continuous transitions, thus making the display feasible for augmented reality. In particular, we compensate the intensity variations, we ensure a consistent horizontal parallax within and between the adjacent viewing zones, and we add vertical parallax. In this way, the display becomes a transparent augmented window that can be used for various augmented reality applications. We present results on a display with 5 viewing zones for three different use cases, evaluate the appropriateness, discuss the limitations, and show future directions.

Article tiré d'une communication du congrès MMA 2021 - 14th International scientific conference MMA 2021 - Flexible technologies; International audience; Combination of In-situ Resource Utilization (ISRU) and on-site Additive Manufacturing (AM) is one of the “outer space applied technologies” candidates where free shape fabrication from micro (e.g., tools) to mega scale (e.g. lunar habitats) will allow in coming future to settle the Moon or potentially other celestial bodies. Within this research, Selected Laser Melting (SLM) of lunar soil (regolith) simulants (LHS-1 LMS-1 and JSC-2A) using a continuous wave 100 W 1090 nm fiber laser was applied. The resulting samples were mechanically and optically characterized. A numerical multiphysics model was developed to understand the heat transfer and optimize the SLM process. Results obtained are in good agreement with the numerical model. The physical and chemical characteristics of the various materials (granulometry, density, composition, and thermal properties) have a strong impact on the AM parameters.

International audience; Integration of photonic structures in nanocrystal-based photodetectors has been demonstrated to improve device performances. Furthermore, bias-dependent photoresponse can be observed in such devices as a result of the interplay between hopping transport and inhomogeneous electromagnetic field. Here, we investigate the main physical concepts leading to a voltage-dependent photoresponse. We first bring evidence of bias-dependent carrier mobilities in a nanocrystal array over a wide range of temperatures. Then, we realize an infrared sensing device using HgTe nanocrystals, where the electrodes also play the role of a grating, inducing a spatially inhomogeneous absorption. The obtained device exhibits a significant bias-dependent photoresponse while possessing a competitive detection performance in the extended shortwave and mid-wave infrared, with detectivity reaching 7x10 10 Jones at 80 K and a fast response time of around 70 ns. This work provides the foundation for further advancements in nanocrystal-basedactive photonics devices.

International audience; The frequency chirping properties of silicon ring resonator modulators (RRMs) are experimentally investigated under sinusoidal modulation. The modulated electric field at the output of an RRM is measured in the time domain thanks to a coherent detection system. The power and phase waveforms are then analyzed in terms of their temporal phase and amplitude for different wavelength detunings between the optical source and the resonance and for different modulation frequencies. The evolution of the frequency chirp, described through a peak-to-peak chirp parameter, is quantified as a function of wavelength detuning and modulation frequency for the first time.

International audience; We present here a demonstration of THz transmission system enabling a full frequency duplex link in the 300 GHz band. This system is coupling a super-heterodyne architecture, E-band modems and duplexing system at 300 GHz.; Nous présentons ici une démonstration d'un système de transmission THz permettant une liaison fréquentielle bidirectionnelle simultanée dans la bande des 300 GHz. Ce système associe une architecture super-hétérodyne, des modems en bande E et un système de duplexage à 300 GHz.

National audience; The understanding and analyzing of solid particle behavior in a liquid is a challenge in numerouse fields and engineering industry as the petroleum or the cosmetic one. It is indeed essential to know the behavior of soft matter process to avoid problems and ensures the product quality. This study presents the viscosimeter development working on a resonant optical signal principle by measuring the Free Spectral Range (FSR) parameter of a resonant optical mode during nanoparticles (NPs) sedimentation in a liquid which consists of a water/glycerol mixture. The photonic structure is composed of racetracks micro-resonators made of a UV210 polymer fabricated by deep-UV photolitography developped on an oxydated silicon layer to get a Si/SiO2 bi-layer. The chip is then integrated in an optical bench to track the evolution of the FSR during the complet sedimentation process. The resonant signal analyse established by an adapted signal processing of silica nanoparticles sedimentation in different water/glycerol concentrations allows us to determine stages and velocity rate of the sedimentation process to finaly access to their viscosity. At the same time, measures are performed on a commercial mechanical rheometer so as to compare the dynamic evolution of their viscosity and their associated FSR. The plot of those data versus the glycerol concentration in water obviously shows a possible mathematical transformation between viscosity and FSR slope. There is therefore a good agreement between mechanical and resonant optical measures ; so this work proves the feasability of an optical viscosimeter based on resonant signal.

International audience; In this work, we introduce a novel approach for depth estimation in a computer-generated hologram by employing horizontal segmentation of the reconstruction volume instead of conventional vertical segmentation. The reconstruction volume is divided into horizontal slices and each slice is processed using a residual U-net architecture to identify in-focus lines, enabling determination of the slice’s intersection with the 3D scene. The individual slice results are then combined to generate a dense depth map of the scene. Our experiments demonstrate the effectiveness of our method, with improved accuracy, faster processing times, lower graphics processing unit (GPU) utilization, and smoother predicted depth maps than existing state-of-the-art models.

International audience; The direct epitaxy of III-V lasers on Silicon (Si) substrates has been considered for decades as an important objective for the realization of integrated photonics chips. However, the difference in crystal structure, lattice-constant, thermal expansion coefficient as well as issues related to the reactivity of the Si surface have made this topic extremely challenging. For that reason, the direct epitaxy of lasers having good performance and decent lifetime on Si was considered as an almost unattainable dream, and many labs and companies have thus developed ways to circumvent this issue using hybridization techniques. However, major progress has been achieved recently thanks to a better understanding of the defect generation mechanisms, and systematic studies of their suppression [1], or at least the drastic reduction of their density into the active region of the device. In this presentation, we will discuss the challenges related to the growth of III-Vs on Si as well as the progress made lately in that field. We will then discuss the current state-of-the-art of mid-IR lasers grown on Si [2]. GaSb diode lasers (DLs) with GaInAsSb/AlGaAsSb quantum well active zones emitting near 2.3 µm exhibit record threshold current-densities near 200 A.cm-2. Their threshold current density is however sensitive to the threading-dislocation density that generate non radiative recombination [3,4]. In contrast, InAs/AlSb quantum cascade lasers emitting near 8 µm demonstrated performances similar to those on native InAs substrates, thanks to the short radiative lifetimes and the unipolar nature of the radiative process [5]. Finally, at intermediate wavelength (3.5 µm), InAs/GaInSb type-II interband cascade lasers also proved to be relatively insensitive to dislocations, which is ascribed to their particular band structure, their performance being similar to those achieved on native GaSb substrates [6]. These results open the route to active photonic integrated circuits operating in the mid-infrared for sensing applications [7].

An all-fiber coupled laser heterodyne radiometer (LHR), using a wideband tunable external cavity diode laser (1500–1640 nm) as local oscillator laser, was developed for ground-based remote sensing of carbon dioxide. Optimal absorption lines and transmission spectra of carbon dioxide in this wavelength range were determined. High sensitivity of the LHR was achieved by using a balanced photodetector to suppress the relative intensity noise of the local oscillator laser. The noise model of the highly sensitive LHR was analyzed and compared with the traditional LHR using single photodetector [1-2]. Finally, field campaigns were performed on the roof of the platform of IRENE building in Dunkerque (51.05°N/2.34°E). The measured LHR spectra in the atmospheric column are compared, in good agreement, with referenced Fourier-transform infrared spectra from the TCCON observation network and with the simulation spectra resulting from an atmospheric transmission modeling. Experimental details including noise analysis and LHR spectra will be discussed and presented. AcknowledgmentsThe authors thank the financial supports from the LABEX CaPPA project (ANR-10-LABX005), the CPER ECRIN program, the EU H2020-ATMOS project as well as the funding from China Scholarship Council (CSC). References[1] T. G. Blaney. "Signal-to-noise ratio and other characteristics of heterodyne radiation receivers", Space Science Reviews 17 (1975) 691-702.[2] F. Shen, G. Wang, J. Wang, T. Tan, G. Wang, P. Jeseck, Y.-V. Te, X. Gao, W. Chen. "A transportable mid-infrared laser heterodyne radiometer operating in the shot-noise dominated regime", Opt. Lett.46 (2021) 3171-3174.

The pathogenic bacteriaBacillus cereus,Bacillus anthracisandBacillus thuringiensisform spores encased in a protein coat surrounded by a balloon-like exosporium. These structures mediate spore interactions with its environment, including the host immune system, control the transit of molecules that trigger germination and thus are essential for the spore life cycle. Formation of the coat and exosporium has been traditionally visualized by transmission electronic microscopy on fixed cells. Recently, we showed that assembly of the exosporium can be directly observed in liveB. cereuscells by super resolution-structured illumination microscopy (SR-SIM) using the membrane MitoTrackerGreen (MTG) dye. Here, we demonstrate that the different steps of coat formation can also be visualized by SR-SIM using MTG and SNAP-cell TMR-star dyes duringB. cereussporulation. We used these markers to characterize a subpopulation of engulfment-defectiveB. cereuscells that develops at a suboptimal sporulation temperature. Importantly, we predicted and confirmed that synthesis and accumulation of coat material, as well as synthesis of the σK-dependent protein BxpB, occur in cells arrested during engulfment. These results suggest that, unlike the well-studied model organismBacillus subtilis, the activity of σKis not strictly linked to the state of forespore development inB. cereus.

International audience; This paper proposes a novel code for optical code division multiple access (OCDMA) systems, called the three-dimensional (3D) spectral/temporal/spatial single weight zero cross-correlation (3D-SWZCC) code. The proposed code could potentially be used in the next generation of passive optical networks (NG-PONs) to provide a 3D-SWZCC-OCDMA-NG-PON system. The developed code has a high capacity and a zero cross-correlation property that completely suppresses the multiple access interference (MAI) effects that are a main drawback for OCDMA systems. Previously, a two-dimensional (2D) SWZCC code was proposed for two-dimensional OCDMA (2D-OCDMA) systems. It works by devoting the first and second components to spectral and spatial encodings, respectively. However, the proposed code aims to carry out encoding domains in spectral, time, and spatial aspects for the first, second, and third components, respectively. One-dimensional, 2D, and 3D systems can support up to 68, 157, and 454 active users with total code lengths equal to 68, 171, and 273, respectively. Numerical results reveal that the 3D-SWZCC code outperforms codes from previous studies, including 3D codes such as perfect difference (PD), PD/multi-diagonal (PD/MD), dynamic cyclic shift/MD (DCS/MD), and Pascal’s triangle zero cross-correlation (PTZCC), according to various metrics. The system function is provided by exhibiting the architecture of the transmitter and receiver in the PON context, where the proposed code demonstrates its effectiveness in meeting optical communication requirements based on 3D-OCDMA-PON by producing a high quality factor (Q) of 18.8 and low bit error rate (BER) of 3.48 × 10−29 over a long distance that can reach 30 Km for a data rate of 0.622 Gbps.

The present article discusses the investigation of CuIn Ga S (CIGS) thin films for photovoltaic applications. For decades, a Cu-rich composition has been used to create solar cells with efficiencies of up to 13.5%; however, interest in chalcopyrite sulfide has recently been revived due to its high and adjustable bandgap, making it a serious candidate as a top cell in tandem configurations. Although chalcopyrite selenides share many properties with CIGS thin films, crucial differences have been reported. To further understand these materials, we studied more than 500 samples of absorbers and resulting solar cells. First, we found that the compositional window for obtaining single-phase CIGS thin films with a 3-stage co-evaporation process is very narrow. Second, we reported that a combination of low copper content and sodium addition during growth is required to maximize the Photoluminescence intensity ( i.e. to minimize the absorber-related open-circuit voltage losses). Finally, we showed that solar cell performance and stability depend not only on absorber quality but also on phenomena at interfaces (absorber/buffer and grain boundaries). Altogether, we formulate growth recommendations for the manufacture of stable CIGS/CdS solar cells with state-of-the-art efficiency.

Today, one of the biological problems is electromagnetic pollution in the environment. The intensity of electromagnetic radiation is so pervasive that it is now known as a form of latent and silent pollution. The study of the biological effects of these waves on the growth and development of living insects - such as bees - are considered by many scientific communities around the world. However, the response of honey/wild bees to traps designed to selectively stimulate bee light receptors by fluorescent light indicated that selective arousal of the blue light receptor type was highly attractive. In this paper, to selectively stimulate the blue light receiver in bee species in order to guide the bee navigation system to return to its hive and prevent the colony collapse disorder (CCD) phenomenon, high-efficiency continuous laser emission by second-harmonic line width of 456 nm Nd:GdVO4 laser is proposed.

THe WEST Team: http://west.cea.fr/WESTteam; International audience; Plasma facing components temperature measurement is required to ensure safe high power for long pulse tokamak operation and for physics studies. During the WEST phase 1, a set of 20 thermocouples (TC) and 4 fibers Bragg grating (FBG) have been exposed to five experimental campaigns with 3889 plasmas for a total plasma duration of about 7h15 and 21.2 GJ of cumulated injected energy. This paper presents the performances in terms of response time and high temperature sustaining assess with high heat flux tests performed in the HADES facility. The response time of the TC remains at the same level as before their installation in the divertor. However, the FBG have shown clear increase of their response time depending on the location due to a degradation of the thermal contact of the graphite adhesive and the FBG or component. Finally, one regenerated FBG has been exposed to high temperature, showing that absolute temperature measurement is found reliable up to 1100 °C with the start of some spectrum degradations. Full erasure of the grating is obtained after 10 s at 1200 °C well above the stable temperature of 900 °C of the regenerated FBG.

International audience; The main objective of WEST is to study the behavior of the ITER-like divertor monobloc components, test their resistance and ageing under ITER relevant heat loads.For the upcoming phase 2 of WEST, the lower divertor is now fully equipped with the ITER-like actively cooled bulk tungsten Plasma Facing Units (PFU), designed to withstand 10MW/m2 in steady state. This divertor is also equipped with an enlarged set of ThermoCouples (TCs x 16) and Fiber Bragg Gratings (FBGs) probes (x5) with 14 measurement spots each to evaluate the heat loading during the experiments. This paper presents the new TC and FBG diagnostics as well as the associated inverse method used to estimate the surface heat flux from the embedded temperature measurements in the divertor. The performance of each diagnostic will be evaluated with synthetic measurements generated with realistic heat flux intensity and distribution. The results of a parametrical analysis shows that each diagnostic is able to estimate the spatial distribution of the expected heat fluxes in WEST

International audience; This study shows the design of a low-cost cell-module optical wireless communication system within an electric vehicle battery pack module.The increase in the energy density of the cells is accompanied by increasing constraints on the monitoring of their state. This implies an increase in the number and type of sensors used close to the cells and therefore an increase in the number of connections between the cells' surroundings and the cell monitoring/management system at module level.Wired connections are costly and prone to failure because they are often implemented manually. Monitoring/management systems therefore use distributed sensor systems connected by an isolated wired communication bus of the Daisy Chain type, often offering data rates of up to 1 Mbits.Studies have been carried out on wireless communication systems to replace these Daisy Chains [1]. Some use radio with a simple integration of Bluetooth gateway components [2]. Radio communications can have disadvantages in terms of confidentiality of the data exchanged and resistance to attacks from outside the battery pack.Powerline communication systems have also been proposed. These are sensitive to the noise generated on the power circuit. They are also sensitive to the variation in the impedance of the battery pack, which does not allow the case of advanced battery architectures such as Self Reconfigurable Batteries [3].An optical inter-module communication solution has also been proposed by LION Smart [4]. This solution is based on the same principle as the wired Daisy Chain, i.e. messages are sent back and forth between serial and pack stages. Thus, the data rate is divided as many times as there are communication nodes (one hundred to two hundred times for the case of a battery pack). The proposed solution is based directly on the integration of discrete infrared receiver circuits which do not solve the cost and power constraints.Most of the proposed solutions do not allow the management of events in real time, such as the synchronisation of measurements.This study proposes to investigate the implementation of an optical wireless communication bus between cells and modules that integrates the space, power and cost constraints imposed by this level of integration.The communication bus is based on the principle of open air communication between cells and module by exploiting the empty spaces within the module for light propagation. The environment of a module or even a battery pack offers interesting characteristics in terms of signal-to-noise ratio for light signals. This allows the use of very small and low cost solutions which is an important criterion for cell level integration.The characteristics of the communication bus are asymmetrical in order to take into account the specific constraints of the cell nodes and the module node. In contrast to the cell nodes, the module node is less constrained in terms of compactness and even cost because there are fewer of them in the system.The complexity of receiving an optical message, and therefore its cost and space requirements, increases with the bandwidth used, while the bandwidth of the transmission stage is only slightly affected. Thus, different bandwidths are used for uplink and downlink communications. Module-to-cell downlink communication is limited to a low bandwidth, while cell-to-module communication uses a higher bandwidth.This asymmetry is compensated by another asymmetry in the communication protocols used by the upstream and downstream channels. The slow communication between the module node and the cell nodes is based on periodic broadcast communication. The fast communication between the cell nodes and the module node is based on sequenced point-to-point communication.The broadcast communications from the module node are used as a time reference for the synchronisation of the sequential cell-to-module communications, thus reducing the clock accuracy constraints applied to the cell node sufficiently to avoid the need to use expensive time references such as crystal oscillators.A higher level protocol is then developed. This protocol is based on the request and answer principle. Each request and answer consists of a frame of several bytes including addressing and integrity information (in the form of an error checking code). The module node interrogates the cell nodes with a broadcast request addressing either a specific cell node or all the cell nodes (depending on the address contained in the question frame). The nodes concerned then respond in their respective slot times according to the nature of the request.A prototype of the communication bus that meets the integration constraints of a 12-cell pouch cell battery module has been realized. This prototype consists of 12 cell communication nodes and one module-level communication node. The open air propagation channel for the optical communications is made with a cross-section of 7x21mm over a length of 200mm. Each cell node is spaced at a distance of between 12 and 17mm.The cell communication nodes are implemented with a target component cost of less than $1 per cell (including encoding, transmitting, decoding, receiving, voltage and temperature measurement stages, an MCU monitoring the cell parameters and powering all these elements). The resulting bandwidths are 115.2kbits module to cell and 1.14Mbits cell to module with a minimum request-answers period of 10 ms.Tests of a low cost reflective coating were also carried out on one side of the propagation channel with improvements of around 40% on the amplitude of the optical signal.This work is part of the European Cobra project and will be used to produce 3 automotive modules of 12 cobalt-free cells equipped with advanced near-cell sensors.References[1] S. S. W. S. Samanta, «A Survey of Wireless Battery Management System: Topology, Emerging Trends, and Challenges,» Electronics, vol. 10, n° %118, p. 2193, 2021. [2] J. F. e. al., «Wireless Battery Management System for Safe High-Capacity Energy Storage,» Materials Research Society, San Francisco, CA, United States, 2014.[3] R. T. e. al., «A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation,» World Electric Vehicle Journal, vol. 12, n° %11, p. 8, 2021. [4] Lion SMART, «NEW BATTERY CONCEPT LIGHT BATTERY MODULAR, SAFE AND WIRELESS,» 05 06 2018. [En ligne]. Available: https://lionsmart.com/en/new-battery-concept-light-battery-modular-safe-and-wireless/.

We present the simulation, fabrication, and characterization of large area microstructured fiber tapers which enables broadband phasematching conditions of the four wave-mixing process. These silica-based tapers are intended to serve as a nonlinear gain medium for intense and high average power Fiber Optical Parametric Chirped Pulse Amplifier emitting at 2 $$\upmu \hbox {m}$$ μ m and strongly pumped at Yb wavelength. Different geometries (tapered/untapered, aspect ratio, etc.) are fabricated, analyzed and their broadening properties—key for supporting ultrashort pulses amplification—are compared and discussed. The characterization of nonlinear gain bandwidth of the tapers relies on a tunable source of stochastic pulses based on tunable amplified spontaneous emission in Yb-doped amplifiers. The strong overshoots of this source allows degenerate four-wave mixing process to occur thus generating broadband incoherent visible signal and mid-infrared idler waves at much lower average power than usually needed with coherent pumping. The idler centered around 1.85 $$\mu$$ μ m is broadened due to zero-dispersion wavelength shift along the taper.

Ultrafast laser processing can induce surface nanostructurating (SNS) in most materials with dimensions close to the irradiation laser wavelength. In-situ SNS characterization could be key for laser parameter's fine-tuning, essential for the generation of complex and/or hybrid nanostructures. Laser Induced Periodic Surface Structures (LIPSS) created in the ultraviolet (UV) range generate the most fascinating effects. They are however highly challenging to characterize in a non-destructive manner since their dimensions can be as small as 100 nm. Conventional optical imaging methods are indeed limited by diffraction to a resolution of ≈ 150 nm. Although optical super-resolution techniques can go beyond the diffraction limit, which in theory allows the visualization of LIPSS, most super-resolution methods require the presence of small probes (such as fluorophores) which modifies the sample and is usually incompatible with a direct surface inspection. In this paper, we demonstrate that a modified label-free Confocal Reflectance Microscope (CRM) in a photon reassignment regime (also called re-scan microscopy) can detect sub-diffraction limit LIPSS. SNS generated on a titanium sample irradiated with a λ =257 nm femtosecond UV-laser were characterized with nanostructuring period ranging from 105 nm to 172 nm. Our label-free, non-destructive optical surface inspection was done at 180µm²/s, and the results are compared with commercial SEM showing the metrological efficiency of our approach., L'interaction entre un laser ultrarapide et une objet peut induire une nanostructuration de surface (NSS) dans la plupart des matériaux, avec des dimensions proches de la longueur d'onde du laser d'irradiation. La caractérisation de NSS in-situ pourrait être la clé permettant un réglage fin des paramètres lasers, essentiel pour la génération de nanostructures complexes et/ou hybrides. Les structures de surface périodiques induites par laser (LIPSS) générées par une illumination ultraviolette (UV) génèrent les effets les plus fascinants. Ils sont cependant très difficiles à caractériser de manière non destructive puisque leurs dimensions descendre à 100 nm. Les méthodes d'imagerie optique classiques sont en effet limitées par la diffraction à une résolution de ≈ 150 nm. Bien que les techniques de super-résolution optique puissent aller au-delà de la limite de diffraction, ce qui permet en théorie la visualisation de LIPSS, la plupart des méthodes de super-résolution nécessitent la présence de petites sondes (comme des fluorophores) qui modifient l'échantillon et sont généralement incompatibles avec une imagerie directe des surfaces. Dans cet article, nous démontrons qu'un microscope confocale en réflectance sans marquage (CRM) dans un régime de réallocation de photons (également appelé microscopie de re-scan) peut détecter des LIPSS spis la limite de diffraction. Les NSS générées sur un échantillon de titane irradié avec un laser UV femtoseconde λ = 257 nm ont été caractérisés avec une période de nanostructuration allant de 105 nm à 172 nm. Notre inspection de surface optique sans marquage et non destructive a été effectuée à 180 µm²/s, et les résultats sont comparés avec un MEB commercial montrant l'efficacité métrologique de notre approche.

International audience; Migration and sedimentation of solid particles in a liquid are physical phenomena involving accumulation of soft matter or decantation of fragmented matter. A thorough understanding together with relevant measurements are prerequisites regarding many fields, including medicine, galenic pharmacology, food processing, and the cosmetics industry. In this paper, we investigate the feasibility of monitoring and detecting the migration of a nanoparticle cloud with a resonant light probe. For this purpose, hybrid silicon/silica/UV210 organic integrated photonic racetrack resonators were patterned by thin film processes to be used as sensors measuring the outcome of the impact of a cloud of nanoparticles, the dynamic migration plus sedimentation phenomenon of the nanoparticle cloud in water. A broadband superluminescent diode has been used for the excitation. Then, the spectral characteristics of the resonant guided modes have been analyzed, considering the observed changes while tracking the free spectral range of the transduced comb spectra as a function of time. The way to operate can be summarized as follows: Solutions based on spherical silica nanoparticles of fixed size are prepared and subjected to rheological measurements to obtain their respective viscosities. Next, a millimeter tank filled with water is conveniently placed on the active surface of the sensing chip, prior to the addition of one of the previously mentioned solutions. The series of spectra are acquired during the whole migration sequence and the transduced optical signal is then directly processed and treated by a specific code operated in real time by way of Lagrange interpolation polynomials. Collected data are then compared to a simple theoretical model describing the sedimentation of a spherical particle in water (Stokes' law). Eventually, the implementation of the device in a characterization platform and the development of a specific protocol allows a global treatment, whose description is followed by discussions on measurements and data. Consequently, after the impact of the drop containing the nanoparticles, the monitoring of a first phase regarding their fast cloud migration into the global study volume (with flow of matter plus vortex) eventually followed by their slow sedimentation, can be detected using such a resonant light probe. The overall duration of the first phase associated with sedimentation velocities is in the order of a few tens of µm/min for particles with submicron diameters (several hundreds of nanometers); a first attempt of comparison of this first phase with the results of the classic Stokes model would give a convergence of the values reaching between 9 and 19% for the sedimentation rates.

The creation of fluorescent defects in silicon is a key stepping stone towards assuring the integration perspectives of quantum photonic devices into existing technologies. Here we demonstrate the creation, by femtosecond laser annealing, of W and G-centers in commercial silicon on insulator (SOI) previously implanted with 12C+ ions. Their quality is comparable to that found for the same emitters obtained with conventional implant processes; as quantified by the photoluminescence radiative lifetime, the broadening of their zero-phonon line (ZPL) and the evolution of these quantities with temperature. In addition to this, we show that both defects can be created without carbon implantation and that we can erase the G-centers by annealing while enhancing the W-centers' emission. These demonstrations are relevant to the deterministic and operando generation of quantum emitters in silicon., 8 pages, 4 figures

International audience

National audience; La navigation basée sur lumière polarisée est une nouvelle forme de navigation exploitant des capteurs bio-inspirées ou conventionnels dans lesquels des attributs du motif de polarisation du ciel sont calculés pour s’orienter ou se localiser. Ce tour d’horizon mettra l’accent sur les progrès de la recherche sur les réalisations de capteurs imageants et non-imageants à des fins de détection de cap. Les méthodes "imageantes" reposent sur des caméras équipées de filtres optiques (statiques ou rotatifs) ou de filtres à grilles métalliques. Aujourd’hui, les caméras dites à division du plan focal (DoFP) sont privilégiées, comme la caméra SONY IMX250MZR [1] pour détecter les axes de symétries ou la correspondance des motifs de polarisation aussi bien en angle de polarisation qu’en degré de polarisation pour en déduire un cap. L’unique boussole optique - SkyPass de Polaris Sensor Technologies, Inc. - disponible sur le marché américain coûte 36000€ pour des applications militaires [2]. Une solution alternative, actuellement émergente, est de coiffer une caméra couleur via une lame d’onde, ce qui permet d’exploiter les propriétés de matériaux biréfringents dont la dépendance de la retardance avec l’incidence des rayons permet de transformer l’état de polarisation en nuances de couleurs : lames à retard en "S" [3] ou linéaire (brevet Stellantis). Les méthodes "non-imageantes" reposent sur l’utilisation de photodiodes surmontées de polariseurs et utilisent, par exemple, le modèle biologique de Thomas Labhart (1988) exploité à bord du robot AntBot [4].RÉFÉRENCES[1] C. Lane, D. Rode, and T. Rösgen, “Calibration of a polarization image sensor and investigation of influencingfactors,” Applied Optics, vol. 61, no. 6, pp. C37–C45, 2022.[2] L. M. Eshelman, A. M. Smith, K. M. Smith, and D. B. Chenault, “Unique navigation solution utilizing sky polarizationsignatures,” in Polarization : Measurement, Analysis, and Remote Sensing XV, vol. 12112, p. 1211203,SPIE, 2022.[3] Y. Fan, R. Zhang, Z. Liu, and J. Chu, “A skylight orientation sensor based on s-waveplate and linear polarizer forautonomous navigation,” IEEE Sensors Journal, vol. 21, no. 20, pp. 23551–23557, 2021.[4] J. Dupeyroux, J. R. Serres, and S. Viollet, “Antbot : A six-legged walking robot able to home like desert ants inoutdoor environments,” Science Robotics, vol. 4, no. 27, p. eaau0307, 2019.

International audience; With the rapid progress in the field of metasurfaces and their use in miniature integrated devices arise the quest for cheap mass production of efficient metasurfaces. We suggest a novel way to design and fabricate phase-gradient Huygens metasurfaces using laser-annealing of uniform particles made of As2S3 chalcogenide glass. We show that a phase gradient metasurface can be realized by tuning the refractive index of otherwise identical meta-atoms instead of tuning their geometry. We are using an array of identical As2S3 particles with the possibility to locally change their refractive index using a short-wavelength illumination (green laser) in order to tune the phase 1 pattern at the post-fabrication stage. Metasurfaces fabricated with this method can be used for operation in the red or IR spectral range. We fabricate uniform As2S3 Huygens metasurfaces using electron beam lithography and demonstrate their post-fabrication tuning with exposure of comparatively low intensity. Samples characterization with transmittance measurement and quantitative phase microscopy provide results in good correspondence with numerical predictions confirming post-fabrication spectral tuning. Using such tuning, we demonstrate the possibility to transfer the intensity pattern produced by modifying a writing beam with a spatial light modulator to a phase pattern recorded on a uniform As2S3 metasurface. Our method has potential advantages for the low-cost production of large-scale metasurfaces because uniform geometries are better adjusted for mass manufacturing.

International audience; The use of nanowires has recently emerged to go further in the development of nitride UV LEDs, especially to improve the efficiency or to make micro-sized UV-sources and flexible LEDs/photodetectors. Our current research interest is focused on the core-shell UV quantum wells grown by industrial MOVPE epitaxy tool. Several types of core-shell quantum wells have been successfully achieved: GaN/InAlN for UV-A, GaN/AlGaN or AlGaN/AlGaN for UV-A and UV-B. When the UV GaN/AlGaN QWs are embedded in a core-shell AlGaN p-n junction, the electroluminescence is demonstrated on single-wire μLEDs in the UV-A and UV-B. The further development of core-shell GaN/AlGaN monolayered system is also shown with demonstration of UV-B emission for single-wire μLEDs.

International audience; Commercialization and industrial deployment of optical feedback interferometry or self-mixing interferometry (SMI)-based displacement instruments are held back due to inaccurate fringe detection under different optical feedback or speckle induced by operating conditions. In this work, we propose using deep neural 2-D networks, which have renowned generalization performance on unseen data. Nonetheless, training deep neural networks requires very large data which in our application would imply acquiring large datasets of experimental signals by operating such interferometers under as many operating conditions as possible. To circumvent this time- and resource-consuming process, we propose a novel data augmentation scheme that increases the amount of training data needed by a deep network for fringe detection/classification in SMI signals. Interestingly, this has enabled the trained deep network to acquire excellent generalization capability where it has learned to detect SMI fringes belonging to weak- and very strong-optical feedback regimes, even when it was only trained on moderate- and strong-feedback regime signals. Consequently, our trained model has shown robust performance for simulated weak-, moderate-, and strong-optical feedback regime SMI signals affected by additive noise. Various experimental SMI signals, acquired under different sensor and optical conditions, have also been successfully processed. We also implemented an established fringe detection method for comparison. Our work presents very good generalization capability when compared to this established method. Our novel augmentation scheme is generic and can be applied to other interferometric signals. We have released our dataset and implementation, with the hope that this will assist the community in accelerating the commercialization of optical feedback interferometry leveraging the full potential of deep learning.

Climate-active gases, notably carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), display fundamental absorption bands in the mid-infrared (mid-IR). The detection and monitoring of those gases could be enabled by the development of mid-IR optical sources. Broadband mid-IR on-chip light emission from rare-earth-doped chalcogenide photonic integrated circuits could provide a compact, efficient, and cost-effective gas sensing solution. Mid-IR photoluminescence of dysprosium-doped selenide ridge waveguides obtained under optical pumping at a telecommunication wavelength (∼1.3 µm) is investigated for Dy3+ ion concentrations in the 2500–10,000 ppmw range. CO2 detection at around 4.3 µm is then demonstrated based on absorption of this broadband mid-IR emission.

International audience

In this paper, we study the spectral efficiency (SE) and energy efficiency (EE) of asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) for visible light communication (VLC). Firstly, we derive the achiev-able rates for Gaussian distributions inputs and practical finite-alphabet inputs. Then, we investigate the SE maximization problems subject to both the total transmit power constraint and the average optical power constraint with the above two inputs, respectively. By exploiting the relationship between the mutual information and the minimum mean-squared error, an optimal power allocation scheme is proposed to maximize the SE with finite-alphabet inputs. To reduce the computational complexity of the power allocation scheme, we derive a closed-form lower bound of the SE. Also, considering the quality of service, we further tackle the non-convex EE maximization problems of ACO-OFDM with the two inputs, respectively. The problems are solved by the proposed Dinkelbach-type iterative algorithm. In each iteration, the interior point algorithm is applied to obtain the optimal power allocation.The performance of the proposed power allocation schemes for the SE and EE maximization are validated through numerical analysis., 14 pages, 10 figures, accepted by IEEE Trans. Wireless Commun

The nanoscale structure of molecular assemblies plays a major role in many (mu)-biological mechanisms. Molecular crystals are one of the most simple of these assemblies and are widely used in a variety of applications from pharmaceuticals and agrochemicals, to nutraceuticals and cosmetics. The collective vibrations in such molecular crystals can be probed using terahertz spectroscopy, providing unique characteristic spectral fingerprints. However, the association of the spectral features to the crystal conformation, crystal phase and its environment is a difficult task. We present a combined computational-experimental study on the incorporation of water in lactose molecular crystals, and show how simulations can be used to associate spectral features in the THz region to crystal conformations and phases. Using periodic DFT simulations of lactose molecular crystals, the role of water in the observed lactose THz spectrum is clarified, presenting both direct and indirect contributions. A specific experimental setup is built to allow the controlled heating and corresponding dehydration of the sample, providing the monitoring of the crystal phase transformation dynamics. Besides the observation that lactose phases and phase transformation appear to be more complex than previously thought - including several crystal forms in a single phase and a non-negligible water content in the so-called anhydrous phase - we draw two main conclusions from this study. Firstly, THz modes are spread over more than one molecule and require periodic computation rather than a gas-phase one. Secondly, hydration water does not only play a perturbative role but also participates in the facilitation of the THz vibrations. We thank the referees for their review – it has allowed us to improve the manuscript, and especially the excellent suggestion to check our findings by X-ray diffraction. We thank Dr Florent Blanchard and Dr Pascal Roussel for their kind help with that experiment. This work was partially supported by: (i) the international chair of excellence ‘‘ThOTroV’’ from region ‘‘Hauts-de- France’’; (ii) the welcome talent grant ‘‘NeFiStoV’’ from European metropole of Lille; (iii) the ‘‘TeraStoVe’’ grant from I-site ULNE; (iv) the French government through the National Research Agency (ANR) under program PIA EQUIPEX LEAF ANR-11-EQPX-0025 and ExCELSiOR ANR 11-EQPX-0015; and (v) the French RENATECH network on micro and nanotechnologies. The computational resources and services used in this work were provided by the Centre de Ressources Informatiques (CRI) and by the VSC (Flemisch Supercomputer Center), funded by the Research Foundation Flanders (FWO) and the Flemisch Government – department EWI.

International audience; Producing ultrathin light absorber layers is attractive towards the integration of lightweight planar components in electronic, photonic, and sensor devices. In this work, we report the experimental demonstration of a thin gold (Au) metallic metasurface with near-perfect visible absorption (~ 95 %). Au nanoresonators possessing heights from 5-15 nm with sub-50 nm diameters were engineered by block copolymer (BCP) templating. The Au nanoresonators were fabricated on an alumina (Al2O3) spacer layer and a reflecting Au mirror, in a film-coupled nanoparticle design. The BCP nanopatterning strategy to produce desired heights of Au nanoresonators was tailored to achieve nearperfect absorption at ≈ 600 nm. The experimental insight described in this work is a step forward towards realizing large area flat optics applications derived from subwavelengththin metasurfaces.

International audience; Use of unmanned aerial vehicles (UAVs) to provide on-demand communications has been receiving growing interest, especially for use in remote and hard-to-reach areas. Also, the use of light-emitting diode-based lighting in UAVs has opened opportunities for data transmission through visible-light communications. To manage multiuser interference while avoiding complex handover procedures, we consider the use of zero forcing (ZF) pre-coding. Since the performance of ZF pre-coding depends on the correlation between channel gains of users, we propose in this paper to reduce it by means of location optimization of UAVs. More specifically, we use particle swarm optimization with the objective of maximizing the overall achievable network throughput. Furthermore, to relax the optimization requirements at UAVs, we investigate the case when the optimization is performed at a specific rate under different mobility conditions.

International audience; Infrared optoelectronics is driven by epitaxially grown semiconductors and the introduction of alternative materials is often viewed with some suspicion until the newcomer has demonstrated a high degree of viability. Infrared nanocrystals have certainly reached this degree of maturity switching from the demonstration of absorption by chemists to their integration into increasingly complex systems. Here, we review some of the recent developments relative to the integration of nanocrystal devices in the 1-5 µm range.