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We report on the use of hollow-core photonic crystal fibers to monitor the evolution of chemical reactions. The combination of tight confinement and long interaction length allows single-pass spect...

International audience; In this paper, a bandpass filter realized on a flexible substrate made of a cellulose-based material is presented. The operating frequency band is selected in order to address industrial, scientific and medical (ISM) applications. The bandpass filter central frequency is equal to 2.45 GHz. The filter design exploits a quasilumped microstrip structure and the circuit realized from a copper adhesive laminate is shaped by laser. The bio-sourced material is a cellulose ester. The characterization of the proposed filter demonstrates that measurement and simulation data are in a very good agreement.

Short wavelength light sources in the blue and ultraviolet (UV) are extremely useful for applications such as semiconductor metrology, photolithography, molecular spectroscopy and high performance liquid chromatography [1] . Gas-filled single-ring hollow-core photonic crystal fibre (SR-PCF), guiding by anti-resonant-reflection, is highly suitable for efficient generation of broadband supercontinua and tunable narrowband UV light because its nonlinearity and dispersion can be tuned by varying the species and pressure of gas [2] . We report the use of tapered SR-PCF filled with 15 bar krypton, pumped with ultrashort (220 fs) 1030 nm pulses carrying 7.8 μJ of energy from a compact laser source, to extend the UV bandwidth and achieve significant spectral power in the 200-350 nm region. The pulses are launched into the untapered end of a SR-PCF with core diameter of 36 μm and an average core-wall thickness of 386 nm (standard deviation 23 nm). Anti-crossings between the core modes and the resonances in the cladding walls result in loss peaks that interrupt the broad transmission window of the SRPCF. Upon propagation, the pulses break up due to modulational instability, resulting in a broad supercontinuum, the blue side of which forms by dispersive wave (DW) emission. By tapering the SR-PCF to half its original dimensions, the phase-matching wavelength for DW emission shifts to higher frequencies [3] , following the shift in zero dispersion wavelength indicated in Fig. 1(a) by dashed lines. As the thickness of the capillary walls falls, the loss peaks (marked by the shaded grey areas in Fig. 1(b) ) shift further into the blue, as previously reported [4] . As a result, the generated UV band extends down to 220 nm in the tapered fibre, a considerable improvement over untapered fibre, where the high frequency edge ends at 310 nm ( Fig. 1(a) ). The tapers were fabricated by brushing an oxy-butane flame across the fibre while pulling it apart axially, keeping the core at near vacuum pressure (60 mbar) and the cladding capillaries at atmospheric pressure [4] . The insets in Fig. 1(b) show optical micrographs of the untapered (above) and tapered (below) ends of the SR-PCF.

Photon pairs (biphotons) are ubiquitous in quantum technologies. In particular, in quantum imaging and spectroscopy they enable measurements in hard-to-access spectral ranges [1] and increased sensitivity [2] . Among different sources of biphotons, four-wave mixing (FWM) in optical fibers is most efficient due to the large nonlinear interaction lengths and easy integrability into optical networks. However, fiber sources are usually not tuneable except by tuning the pump wavelength. Hollow-core photonic crystals fibers (PCF) filled by noble gas solve this problem: their dispersion landscape can be tailored by simply changing the gas pressure [3] , [4] . Additionally, they are free from Raman scattering and have a higher damage threshold than solid-core fibers [4] .

Tunable biphotons are highly important for a wide range of quantum applications. For some applications, especially interesting are cases where two photons of a pair are far apart in frequency. Here, we report a tunable biphoton source based on a xenon-filled hollow-core photonic crystal fiber. Tunability is achieved by adjusting the pressure of the gas inside the fiber. This allows us to tailor the dispersion landscape of the fiber, overcoming the principal limitations of solid-core fiber-based biphoton sources. We report a maximum tunability of 120 THz for a pressure range of 4 bar with a continuous shift of 30 THz/bar. At 21 bar, the photons of a pair are separated by more than one octave. Despite the large separation, both photons have large bandwidths. At 17 bar, they form a very broad (110 THz) band around the frequency of the pump., 5 pages, 4 figures

Application of polymer-flooding systems in secondary and tertiary oil recovery represents a real challenge for oil industry. In this work, our main objective is to explore possibilities of making use of xanthan-g-polyacrylamide for polymer flooding in a particular Devonian oilfield of medium salinity. The graft polymer was synthesized by using microwave-assisted graft copolymerization reaction of acrylamide on xanthan. The synthesized copolymer with optimized grafting parameters has been characterized by Infrared Spectroscopy and Thermal Analysis (DSC). Rheological analysis by steady shear and oscillatory flow experiments have been subsequently performed for xanthan and grafted xanthan under reservoir conditions. In steady shear, as expected the grafted polymer solutions flow as shear-thinning materials and apparent viscosity showed good fits with Cross’s model. The viscosity losses due to salinity or temperature are more controlled for the grafted xanthan compared to pristine xanthan. When the grafted polymer concentration is increased to 2000 ppm the losses were halved. In oscillatory shear, the copolymer solutions followed a global behavior of semi-dilute entangled systems, furthermore, all dynamic properties were influenced by the brine salinity. Compared to xanthan, the elastic properties of xanthan-g-polyacrylamide solutions have been significantly improved in saline media and the losses in elasticity of grafted polymer solutions are lower.

International audience; The capability of some polymers, such as chitosan, to form low cost gels under mild conditions is of great application interest. Ionotropic gelation of chitosan has been used predominantly for the preparation of gel beads for biomedical application. Only in the last few years has the use of this method been extended to the fabrication of chitosan-based flat structures. Herein, after an initial analysis of the major applications of chitosan flat membranes and films and their usual methods of synthesis, the process of ionotropic gelation of chitosan and some recently proposed novel procedures for the synthesis of flat structures are presented.

International audience; The objective of the paper is to provide a suitable analytical approach to describe the behaviour of a square miniaturised (MEMS) receiving transducer made up of a square membrane having the same dimensions as the external dimensions of the transducer itself, loaded by both a thin square small sized fluid-gap and a peripheral cavity connected together and set rear the membrane. This device departs from the other previous square devices in that the peripheral cavity is rear the membrane at the periphery of the backing plate (backing electrode). This architecture (derived from the circular one suggested previously) enables to optimize the sensitivity of the transducer while retaining both a cartesian geometry and the smallest dimensions possible (surface area and thickness). The analytical approach accounting for the effects of the interior geometrical discontinuity on the displacement field of the membrane used here to describe such square transducers (electrostatic or piezoelectric) departs from previous ones in that it avoids multi-modal analysis which exhibits procedural difficulties due to the coupling of Dirichlet-like (membrane) and Neumann-like (fluid) eigenfunctions (emphasized here by presence of the geometrical discontinuity in the fluid-filled part of the device). Additionally, an approximate analytical solution appropriate to express the displacement field of the membrane and to estimate the sensitivity with a good accuracy in the lower frequency range is presented. FEM solutions are provided, against which the analytical results have been tested.

International audience; Identification of elastic and damping properties is a challenge for fabrication of composite materials, which can have complex shapes. A new approach based on the Force Analysis Technique was developed to identify structural parameters from local equation of motion. For structures with known analytical models, this method gave good results. This work presents a similar approach to extend the previous method to structures which cannot be described with known analytical models, where the model is replaced by a Finite Element operator. In order to reduce the amplification of the measurement noise, a procedure based on a probabilistic approach coupled to a minimization of a cost function is proposed. The method is illustrated on a curved beam using simulated displacement. Then, an experimental validation is shown by using measured translations on an aluminum flat beam and on a sandwich curved beam.

We present the use of linearly down-tapered gas-filled hollow-core photonic crystal fiber in a single-stage, pumped with pulses from a compact infrared laser source, to generate a supercontinuum carrying significant spectral power in the deep ultraviolet (200 - 300 nm). The generated supercontinuum extends from the near infrared down to around 213 nm with up to 0.83 mW/nm in the deep ultraviolet., Comment: 4 pages (+1 page for full reference list), 3 figures

Hyperspectral stimulated Raman scattering (SRS) microscopy is a powerful label-free, chemical-specific technique for biomedical and mineralogical imaging. Usually, broad and rapid spectral scanning across Raman bands is required for species identification. In many implementations, however, the Raman spectral scan speed is limited by the need to tune source laser wavelengths. Alternatively, a broadband supercontinuum source can be considered. In SRS microscopy, however, source noise is critically important, precluding many spectral broadening schemes. Here we show that a supercontinuum light source based on all normal dispersion (ANDi) fibres provides a stable broadband output with very low incremental source noise. We characterized the noise power spectral density of the ANDi fibre output and demonstrated its use in hyperspectral SRS microscopy applications. This confirms the viability and ease of implementation of ANDi fibre sources tier broadband SRS imaging. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

In this article, the dielectric properties of a biosourced polymer are investigated. To that end, coplanar transmission lines were fabricated on a 600- $\mu \text{m}$ thick cellulose palmitate substrate by using a photolithographic process and a transfer technique. The ${S}$ -parameters of the transmission lines were measured in a broad microwave frequency band spanning from 10 to 67 GHz in order to determine the propagation constant. From these data, the complex dielectric permittivity was extracted by using two analytical methods (RLCG method, based on resistance, inductance, capacitance and conductance of transmission lines and conformal mapping method) and a numerical one [finite element method (FEM)]. The three methods allow distinguishing the dielectric losses from the total measured losses of the transmission lines. Finally, the dielectric constant and the loss tangent of this biopolymer were compared to the data of common and commercially available substrates: polyimide and polyethylene naphthalate.

We monitor the reaction of an acid with an alcohol inside a hollow-core photonic crystal fibre using Raman spectroscopy. The method uses tiny amount of chemicals and allows precise measurement of the activation energy.

We report non-destructive measurement of the diameter of submicron air-clad waveguides to nanometer precision, based on parametric amplification of a broadband seed signal. Ultrashort pump and seed pulses allow the diameter to be longitudinally resolved.

Four-wave mixing in Ar-filled sub-micron suspended-core fibres is used to generate spectrally tunable entangled photon pairs. A continuous shift of 0.30 THz/bar is measured for the generated sidebands with a coincidence-to-accidental ratio over 104.

International audience; Polylactic acid (PLA) is a bio-based and biodegradable polymer currently used in a wide range of packaging, medical, and industrial applications. PLA is also envisaged for the development of sustainable products for general public, including electronic devices. For these applications, the knowledge of the dielectric properties is required, in particular for high frequency electronics. In this letter, coplanar waveguides are realized on a PLA substrate in order to characterize its complex permittivity from 0.5 to 67 GHz. To avoid putting the PLA in contact with strong chemicals or solvents, a line transfer technique combined with photolithography process has been developed to realize the test structure. The propagation constant is calculated by de-embedding techniques using S-parameter measurements. Finally, finite element method analysis is used to determine the real permittivity (epsilon(r)) and loss tangent (tan delta) of the PLA substrate.

We compare the properties of the broadband supercontinuum (SC) generated in twisted and untwisted solid-core photonic crystal fibers when pumped by circularly polarized 40 picosecond laser pulses at 1064 nm. In the helically twisted fiber, fabricated by spinning the preform during the draw, the SC is robustly circularly polarized across its entire spectrum whereas, in the straight fiber, axial fluctuations in linear birefringence and polarization-dependent nonlinear effects cause the polarization state to vary randomly with the wavelength. Theoretical modelling confirms the experimental results. Helically twisted photonic crystal fibers permit the generation of pure circularly polarized SC light with excellent polarization stability against fluctuations in input power and environmental perturbations.

cited By 0; International audience; In this work, the dielectric properties of a biosourced polymer are investigated. To that end, coplanar transmission lines were fabricated on a 600 μm thick cellulose palmitate substrate by using a transfer technique and photolithography. Then, the S-parameters of the transmission lines were measured in a broad microwave frequency band spanning from 0,5 to 67 GHz. Finally, the propagation constant was determined and the complex effective permittivity was extracted.

Supercontinuum (SC) generation in solid-core photonic crystal fibres (PCFs) is well established and has diverse applications in science and technology [1,2]. In a conventional SC, the polarization state is not maintained over the whole spectrum due to cross-phase modulation and may in addition vary with power. Recently, it has been reported that continuously twisted PCFs exhibit circular birefringence [3,4]. Here we report the first experimental demonstration of a twisted PCF that robustly maintains circular polarization state across the whole spectrum, independent of power.

We demonstrate the use a low noise all-normal-dispersion nonlinear fiber as a supercontinuum light source for Hyperspectral Stimulated Raman Scattering microscopy., 2019 Photonics North (PN), May 21-23, 2019, Quebec City, QC, Canada

Non-linear optical microscopy proves to be an indispensable tool in natural sciences and becomes more and more attractive for clinical applications. Coherent Raman scattering, for instance, has the potential to become an in-vivo fast label-free histology tool as its chemical selectivity provides quantitative information on lipids and proteins locations and concentrations in tissues. Along with these techniques, second-harmonic generation of collagen and 2-photon excitation fluorescence broaden even more the non-linear imaging ability as collagen fibers represent an important role in human body construction. Whilst 2-photon excitation fluorescence allows to study auto-fluorescence (ex. NADH and NADHP molecules), and to excite a vast range of chromophores. However, absorption and scattering limit significantly the nonlinear imaging depth into tissues. As a solution, we offer a flexible, compact, and multimodal nonlinear endoscope (2.2 mm outer diameter, 35 mm rigid length) based on a resonantly piezo scanned hollow-core negative curvature double-clad fiber. The fiber design allows distortion-less, background-free delivery of femtosecond excitation pulses and the back-collection of nonlinear signals through the same fiber. The double-cladding of this fiber attends 10^5μm of silica collection surface which allows for a 4-fold collection improvement compared to previously used Kagome hollow core fibers. Having a good control on the resonantly scanning fiber the endoscope can perform nonlinear imaging up to 8 frames per second over a field of view of 400μm. We demonstrate 2photon, SHG and CARS imaging in ex vivo gastric human tissue samples and in-vivo 2-photon fluorescence imaging of GFP-labeled neurons in mouse brain.

International audience; Water Soluble Extracts (WSE) were obtained from Banana Pseudo stems (BPS) using a simple and robust deconstruction procedure. WSE were characterized by FTIR, WAXS, TGA DTG analysis. With the objective of developing fully bio based polymer formulations, WSEfillers were blended to Poly Lactic Acid (PLA) using a solution blending, casting and thermocompression process. Thermal and mechanical properties were investigated by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and uniaxial tensile tests on neat PLA (n–PLA) and PLA/WSE blends at various filler contents. Thermal DSC investigations established that WSE act as a plasticizer on PLA. This was further confirmed by DMA by the shift of the loss factor (tan δ) peak maximum towards lower temperatures. WSE also significantly impacted the thermally induced crystallization of PLA and the nucleating power of WSE was assessed by isothermal and non–isothermal studies. WSE had a detrimental effect on PLA brittleness and a slightly positive in fluence on its stiffness in the glassy state,whereas the drawability remained fairly acceptable when PLA–based materials where drawn at 75 °C above Tg.Moreover, WSE induced an earlier strain–hardening of the composite films as compared to neat PLA. These results underline the valorization potential of such agricultural by products for sustainable polymer applications in the packaging industry.; Des extraits hydrosolubles (WSE) ont été obtenus à partir de pseudo-tiges de banane (BPS) en utilisant une procédure de déconstruction simple et robuste. WSE ont été caractérisées par analyse FTIR, WAXS, TGA DTG. Dans le but de développer des formulations de polymères entièrement à base bio, WSE. Les charges ont été mélangées à de l'acide poly lactique (PLA) en utilisant un procédé de mélange en solution, de coulée et de thermocompression. Les propriétés thermiques et mécaniques ont été étudiées par calorimétrie à balayage différentiel (DSC), analyse mécanique dynamique (DMA) et essais de traction uniaxiale sur des mélanges de PLA (n – PLA) et de PLA / WSE purs à diverses teneurs en charge. Les enquêtes par DSC thermique ont établi que le WSE agissait comme un plastifiant sur le PLA. Cela a été confirmé par DMA par le décalage du maximum du facteur de perte (tan δ) vers des températures plus basses. La WSE a également eu un impact significatif sur la cristallisation induite par la chaleur du PLA et le pouvoir de nucléation de la WSE a été évalué par des études isothermes et non isothermes. WSE a eu un effet néfaste sur la fragilité du PLA et une influence légèrement positive sur sa rigidité à l'état vitreux, tandis que l'aptitude à la traction reste assez acceptable lorsque les matériaux à base de PLA sont étirés à 75 ° C au-dessus de la Tg.De plus, le WSE a induit un durcissement préalable des films composites par rapport au PLA pur. Ces résultats soulignent le potentiel de valorisation de tels produits agricoles pour des applications de polymères durables dans l'industrie de l'emballage.

Banana Pseudo stem (BPS) is an annual renewable agricultural by product with a potential for valorization in the production of paper, textile fibre or new bio–based materials. A gradual deconstruction process was implemented to determine BPS chemical composition and isolate sub–components that may be valorized in the formulation of bio–based polymer composites. At each step, the residues were analyzed by FTIR, X–ray diffraction and TGA–DTG. The chemical composition of the starting material (% of dry weight) was evaluated as:13.4% total extractives, 6% pectins, 14.7% lignins, 28% hemicelluloses and 38% cellulose. The deconstruction process for BPS was efficient but led to mercerized cellulose (cellulose II) as a final residue, as assessed by the intense X–ray scattering peaks centered at 20.5° and 21.5°. Cellulose II formation was induced by the high concentration of the alkaline KOH solution used to dissolve hemicelluloses in holocellulose. The step–wise removal of non cellulosic sub–components led to a more thermally stable residue. Long fibres were also obtained from BPS at a yield of 60%. These fibres display cellulose I structure and a thermal stability similar to the extracted cellulose. SEM analyses of long fibres showed transversal and lateral defects, the presence of surface hairiness and an almost cylindrical morphology. Uniaxial tensile tests were carried out at room temperature on 150 specimens randomly chosen among the less hairy fibres, with diameters ranging from 40 to 140μm.Mechanical investigations (Young modulus: 6.3–26 GPa; nominal stress at break: 140–768 Pa; nominal strain at break:∼3%) reveal a significant disparity strongly influenced by fibre diameter, except for the nominal strain at break which remains fairly constant around 3%. These results are comparable to the upper range of the values reported for fibres extracted from BPS through alternative chemical routes or for fibres obtained from other annual plants such as jute and hemp; La pseudo-tige de banane (BPS) est un produit agricole annuel renouvelable avec un potentiel de valorisation dans la production de papier, de fibre textile ou de nouveaux matériaux biosourcés. Un processus de déconstruction progressive a été mis en œuvre pour déterminer la composition chimique du BPS et isoler les sous – composants susceptibles d'être valorisés dans la formulation de composites polymères biosourcés. À chaque étape, les résidus ont été analysés par FTIR, diffraction des rayons X et TGA – DTG. La composition chimique de la matière de départ (% du poids sec) a été évaluée comme suit:13,4% d'extraits, 6% de pectines, 14,7% de lignines, 28% d'hémicelluloses et 38% de cellulose. Le processus de déconstruction du BPS a été efficace, mais a conduit à la cellulose mercerisée (cellulose II) en tant que résidu final, comme l'indiquent les pics de diffusion des rayons X intenses centrés à 20,5 ° et à 21,5 °. La formation de cellulose II a été induite par la concentration élevée de la solution alcaline de KOH utilisée pour dissoudre les hémicelluloses dans l'holocellulose. L'élimination progressive des sous-composants non cellulosiques a permis d'obtenir un résidu plus stable thermiquement. Des fibres longues ont également été obtenues à partir de BPS avec un rendement de 60%. Ces fibres présentent une structure en cellulose I et une stabilité thermique similaire à celle de la cellulose extraite. Les analyses au MEB de fibres longues ont montré des défauts transversaux et latéraux, la présence de pilosité en surface et une morphologie presque cylindrique. Des tests de traction uniaxiale ont été effectués à température ambiante sur 150 échantillons choisis au hasard parmi les fibres les moins poilues, avec des diamètres allant de 40 à 140 µm.Les investigations mécaniques (module d'Young: 6,3–26 GPa; contrainte nominale à la rupture: 140–768 Pa; contrainte nominale à la rupture: 3%) révèlent une disparité significative fortement influencée par le diamètre de la fibre, à l'exception de la contrainte nominale à la rupture qui reste assez stable constante autour de 3%. Ces résultats sont comparables à la fourchette supérieure des valeurs rapportées pour les fibres extraites du BPS par d'autres voies chimiques ou pour les fibres obtenues d'autres plantes annuelles telles que le jute et le chanvre.

International audience; Modeling a Surface Acoustic Wave (SAW) sensor response as a chemosensor and not only as just an electronic transducer was performed with COMSOL Multiphysics. For this study, the SAW's sensing area was functionalized with an ionic imprinted polymer (IIP), designed for the selective detection of lead ions. The idea consists in subdividing the IIP into elementary blocks whose physical properties can be modified separately. Three configurations have been envisaged: the IIP before and after lead ions extraction and the non-imprinted polymer (NIP). The generation of shear-horizontal waves on LiTaO 3 piezoelectric substrate is confirmed by recording the displacement amplitude versus time, according to the three space directions. The sensors sensitivity is estimated from the delays induced by the incorporation of the lead ions in the IIP layer. To the best of our knowledge, this approach has never been presented in the literature.

Generation of spontaneous third-order down conversion as the reverse of third harmonic generation remains a challenging task, not yet demonstrated. We present different possible strategies involving gas-filled hollow-core photonic crystal fibres, hybrid fibres and tapered fibres in gas.

Direct observation of third-order spontaneous down conversion, where three low energy photons are generated from a single one, remains a challenging task. We report here on different strategies based on engineered optical fibers. These include gas-filled hollow-core photonic crystal fibers, hybrid- and tapered fibers.

We report on fine tuning of phase matching conditions by using high pressure argon gas and demonstrate tunable twin beams in hollow-core photonic crystal fibre and tunable third harmonic generation in tapered fibre.

Third-harmonic phase-matching in tapered silica fiber is tuned by introducing a high pressure gas around the taper waist. This offers a new means of achieving precise control over the dispersion in tapered fibers.

The introduction of techniques such as 3D-printing, extrusion and preform spinning to the drawing of soft-glass nanostructured fibers brings new opportunities. Applications in optomechanics, nonlinear wavelength conversion and laser light delivery will be reviewed.

International audience; The thermal conductivity of flexible biosourced polymers was measured by the 3-omega method. Two biopolymers were investigated: the polylactic acid (PLA), a widely used commercial biodegradable one, and the cellulose palmitate (CP), a hydrophobic biosourced material developed in the laboratory, that could be used in electronic or microfluidic applications. The 3-omega method is based-on the use of a metal element as both heating device to thermally disturb the system and temperature sensor. A stencil lithography technique was applied to obtain metallic lines, since biopolymers are not compatible with classical photolithography method. Thermal conductivities of 0.19 and 0.30 W/m.K are obtained respectively for PLA and CP thick films, and 0.12 and 0.22 W/m.K for respectively PLA and CP thin films. These values are close to those measured for petro-sourced substrates or films and so give the possibility to address the applications mentioned.

Silica-based photonic crystal fibre has proven highly successful for supercontinuum generation, with smooth and flat spectral power densities. However, fused silica glass suffers from strong material absorption in the mid-infrared (>2,500 nm), as well as ultraviolet-related optical damage (solarization), which limits performance and lifetime in the ultraviolet (

cited By 4; International audience; In this work, coplanar transmission lines were fabricated on a polylactic acid substrate. The transmission lines were then characterized in a broad microwave frequency band. From S-parameters measurements, the propagation constant was thus determined allowing the extraction of the complex effective permittivity £* eff

We report on recent advances in soft-glass photonic crystal fibers that make use of improved stack-and-draw and extrusion techniques, and on their use in supercontinuum generation, photochemistry and triplet photon generation.

Two novel kinds of anti-resonant polygonal-core fibers are introduced, including a triangular-core fiber-design with surrounding silica-glass webs [1], and a negatively-curved square-core fiber-design.

Precise modeling of 1D acoustic devices (passive or active, miniaturized or not) containing a planar beam loaded by a fluid gap and cavities is of interest in a variety of applications (transducers, acoustic filters, metamaterials, etc.). An analytical approach presented herein enables the description of the vibration of the planar elastically supported rigid beam of rectangular crossection surrounded by very thin slits and loaded by the fluid gap, which is divided in three parts of different thicknesses (the central part being the thinner one), the thermoviscous losses originating in the fluid being taken into account. Comparing to the case of the fluid gap of uniform thickness, such a geometry provides more parameters which can be adjusted in order to achieve the required behavior (resonant or damped, etc.). The analytically calculated beam displacement is presented and compared to the numerical solution provided by finite element method (a reference against which the analytical results are tested).

We present two optical fibers that are suitable for photon triplet generation: a hybrid fiber that allows phase-matching between single lobed modes and a hollow core kagome fiber that provides pressure-controlled phase-matching.

In order to make concrete construction greener, new High Range Water Reducing Admixtures (HRWRAs) from natural origin-should be developed. Some natural polysaccharides and their derivates have interesting properties which explain their growing use in the field of materials. Their use is not only linked to the biodegradable and atoxic aspect but is also linked to the fact that they can confer new properties to cement-based materials. In the presented study, starch has been chosen as main polysaccharide chain. Starch has first been used without any modification, and then with different grafted substituents like acetate, maleate, succinate, sulfonate to mimic the structure of petrochemical HRWRAs. Some tests have been done to evaluate the potential effect of these biobased derivatives as new HRWRAs. Some of the starch-based polymers were also evaluated in a commercial self-leveling compound. Results show that a graft of sulfopropyle or sulfobutyle side chains on a starch polymer can lead to slump flows on grouts comparable with the ones obtained on PolyNaphtalene Sulfonate (PNS) based grouts, and also that starch-sulfobutyle or starch-maleate can potentially replace casein in self-leveling compounds.

We evaluate prospects, performance and temperature limits of a new approach to macroscopic scale laser refrigeration. The considered refrigeration device is based on exciplex-mediated frequency up-conversion inside hollow-core fibers pressurized with a dopant - buffer gas mixture. Exciplexes are excited molecular states formed by two atoms (dopant and buffer) which do not form a molecule in the ground state but exhibit bound states for electronically excited states. The cooling cycle consists of absorption of laser photons during atomic collisions inducing light assisted exciplex formation followed by blue-shifted spontaneous emission on the atomic line of the bare dopant atoms after molecular separation. This process, closely related to reversing the gain mechanism in excimer lasers, allows for a large fraction of collision energy to be extracted in each cycle. The hollow-core fiber plays a crucial role as it allows for strong light-matter interactions over a long distance, which maximizes the cooling rate per unit volume and the cooling efficiency per injected photon while limiting re-absorption of spontaneously emitted photons channeled into unguided radiation modes. Using quantum optical rate equations and refined dynamical simulations we derive general conditions for efficient cooling of both the gas and subsequently of the surrounding solid state environment. Our analytical approach is applicable to any specific exciplex system considered and reveals the shape of the exciplex potential landscapes as well as the density of the dopant as crucial tuning knobs. The derived scaling laws allow for the identification of optimal exciplex characteristics that help to choose suitable gas mixtures that maximize the refrigeration efficiency for specific applications.We evaluate prospects, performance and temperature limits of a new approach to macroscopic scale laser refrigeration. The considered refrigeration device is based on exciplex-mediated frequency up-conversion inside hollow-core fibers pressurized with a dopant - buffer gas mixture. Exciplexes are excited molecular states formed by two atoms (dopant and buffer) which do not form a molecule in the ground state but exhibit bound states for electronically excited states. The cooling cycle consists of absorption of laser photons during atomic collisions inducing light assisted exciplex formation followed by blue-shifted spontaneous emission on the atomic line of the bare dopant atoms after molecular separation. This process, closely related to reversing the gain mechanism in excimer lasers, allows for a large fraction of collision energy to be extracted in each cycle. The hollow-core fiber plays a crucial role as it allows for strong light-matter interactions over a long distance, which maximizes the cooling ra...

International audience

Over the last two decades the interest in photonic crystal fiber (PCF) has grown considerably, particularly in nonlinear optics where it allows enhanced control over the dispersion landscape. Although silica is the material most commonly used to fabricate PCF, its limited window of transmission and its susceptibility to optical damage at wavelengths below ~350nm is driving the development of fibers made from glasses with transmission windows extending into the deep ultraviolet and the mid-infrared. An alternative is offered by gas-filled hollow-core fiber, in which the light propagates predominantly in the gas. In kagome-style hollow-core PCF filled with noble gas, the weak anomalous dispersion of the empty fiber is balanced by the normal dispersion of the filling gas, resulting in a versatile system whose dispersion landscape can be adjusted in real time [Travers et al., JOSAB 28, A11 (2011)]. Under appropriate conditions the launched pulse undergoes soliton self-compression followed by emission of a band of dispersive radiation in the UV. UV light tunable down to 113 nm has been generated with this technique [Russell et al., Nat. Photon. 8, 278 (2014)]. Solid-core ZBLAN (fluorozirconate) glass PCF is transparent from 0.2 to ~7.8µm. Launching ~1nJ 140fs pulses at 1µm wavelength into a ~1µm diameter core resulted, after 4cm of propagation, in generation of a supercontinuum spectrum extending from ~210nm to beyond 2µm. In strong contrast to silica PCF, the ZBLAN PCF showed no signs of any solarization-related damage, even when operating over many hours [Jiang et al., Nat. Photon. 9, 133 (2015)].

We introduce a new simple design of hollow-core microstructured fiber targeted to guide mid-infrared light at a wavelength 2.94 $ \mu $m. The fiber has a triangular-core supported via silica-glass webs enclosed by a large hollow capillary tube. The fiber specific dimensions are determined based on the guiding technique, which is based on the anti-resonant mechanism. For a triangular-core with side length $100$ $ \mu $m, the fiber has a minimum transmission loss $0.08\pm0.005$ dB/m and dispersion 2.3 ps/km/nm at the operational wavelength 2.94 $ \mu $m.

We present a hybrid photonic-crystal fiber for phase-matched third-harmonic generation. Third-harmonic radiation is confined in a Gaussian-like mode by an all-solid bandgap microstructure, while outer hollow channels ensure guidance of pump radiation in fundamental mode.

We report fabrication of a microstructured ZBLAN fibre with six cores each containing a nanobore of diameter ∼330 nm. Spectral broadening is observed when pumped by 1042 nm pulses in both fundamental and higher order modes.

We successfully demonstrate squeezing of nanosecond pulses via self-induced transparency in a system of mercury vapor confined in a hollow core kagome-style fiber.

Spectral interferometry and dispersive Fourier transformation are combined to retrieve spectral phase information at ~80 MHz in a fiber ring-cavity pumped with ultrashort pulses. Shot-to-shot spectral phase reorganization is observed.

We report recent progress on the fabrication of microstructured fibres from different soft glasses and their use in generating supercontinua in the UV and mid-IR from short-pulse infrared pump lasers at 1 and 2 μm.

A novel simple microstructured fiber with a hollow antiresonant triangular-core is designed, which can reach a minimum transmission loss of 0.08 dB/m and dispersion 2.3 ps/km/nm at a wavelength 2.94 microns.

International audience; Laser ultrasonics was applied to the manufacturing control of the integrity (no failure) of coated spherical particles designed for High Temperature Reactors (HTR). This control is of major importance, since the coating of the nuclear fuel kernel is designed to prevent from the diffusion of fission products outside the particle during reactor operation. The SiC layer composing the coating is particularly important, since this layer must be an impenetrable barrier for fission products. The integrity of the SiC shell (no crack within the shell) can be assessed by the ultrasonic vibration spectrum of the HTR particle, which is significantly changed, compared to the reference spectrum of a defect-free particle. Spheroidal vibration modes of defect-free dummy particles with a zirconium dioxide (ZrO2) core were observed in the 2–5 MHz range. A theoretical analysis is presented to account for the observed vibration spectra of defect-free or cracked HTR particles.