Statistical Description for Assumption-free Single-shot Measurement of Femtosecond Laser Pulse Parameters via Two-photon-induced Photocurrents

Through examining the product of the mathematical variance of intensity with respect to time and frequency, we arrive at a temporal characterization of laser pulses through parameters for pulse duration, group delay dispersion and temporal form. These statistics, which are sufficient to predict subsequent pulse behavior, are recoverable in a simple experiment, measuring the two-photon-induced photocurrents in three nonlinear diodes. With only two photodiodes, we demonstrate that pulse durations as low as several tens of femtoseconds can be easily measured in a single shot if the usual assumptions of pulse form and dispersion are made as in the more difficult autocorrelation setup

Optical Data Storage in Photosensitive Glasses and Spin State Transition Compounds

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HOBIT - un Concept Innovant pour le Transformation des Pratiques Pédagogiques

International audienceHOBIT désigne un nouveau concept destiné à transformer les pratiques pédagogiques concernant l’enseignement de l’optique. Sur une table technique interactive, il permet de placer des composants optiques factices et d’agir sur leurs réglages et de visualiser en temps réel non seulement le phénomène optique résultant mais aussi de bénéficier d'un soutien pédagogique en faisant appel à la réalité augmentée. Nous mettrons l’accent sur la notion de rupture pédagogique qui peut être atteinte avec ce nouveau concept à travers quelques exemples choisis

Spectroscopie LIBS sans calibration (évaluation critique et application à l'analyse de sols pollués)

Aujourd hui encore, malgré l utilisation de techniques spectrochimiques de référence, l aspect quantitatif de la spectroscopie sur plasma induit par laser (LIBS) reste largement en friche du fait d effets de matrice incapacitants. La LIBS sans étalonnage (CF-LIBS) est une des façons considérées par la communauté scientifique afin de relever ce défi. Malgré ses postulats d idéalité du plasma (ETL, homogénéité et stationnarité du plasma), à l heure actuelle peu d études extensives ont été développées afin de réaliser une évaluation critique de la méthode. A l aide d outils théoriques (modèle collisionnel-radiatif développé pour l Aluminium, Argon et Cadmium) et expérimentaux (expérience de Diffusion Thomson) tirant leur origine de la physique des plasmas, ainsi que de cas pratiques d analyses, nous tenterons d établir le cahier des charges le plus favorable à l analyse quantitative par CF-LIBS. L application de cette méthode à l analyse d échantillons complexes (minéraux et sols pollués) sera discutée à l aune de nos résultats et des connaissances actuellement disponibles en la matière.Despite the existence of many benchmarked spectrochemical analysis techniques in the field of Laser-Induced Breakdown Spectroscopy (LIBS), the quantitative analysis holds of the laser induced plasma still holds a huge number of analytical drawbacks, the occurrence of matrix effects not being the slightest among those ones.Calibration-Free LIBS was historically developped to address specifically those aspects, and has already reached a high level of maturation for the analysis of simple metallic or soil samples. Unfortynately, in spite of the strong assumptions that need to be necesserily considered in the CF-LIBS algorithm (such as Local Thermodynamic Equilibrium, and the homogeneity and stationnarity of the plasma), only a few number of contributions have been devoted to the critical assessment of the latter postulates to date. Thanks to the help of several case tests and theoretical (collisionnal-radiative model depicting aluminum, argon and cadmium plasmas) and experimental concepts originating from the field of plasma physics (Thomson-Scattering experiments intended to validate our results), we will focus our study on the research and development of novel experimental criteria that would allow an experimentalist to set up and analyze a CF-LIBS experiment in the least unfavourable theoretical and experimental conditions.We will eventually apply our new considerations on the prediction of the CF-LIBS analysis efficiency, coming to the specific field of interest of analysis of geophysical samples (such as soils polluted by heavy metals). A special interest will be paid on the latest developments appearing nowadays in the field of LIBS, and devote a part of our debate on the expectancies that will have to be fulfilled in order to highen the analysis potential of LIBS.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Dense arrays of microscopic optical vortex generators from femtosecond direct laser writing of radial birefringence in glass

We report on the generation of permanent singular light mode converters at the microscale using femtosecond direct laser writing in photo-thermo-refractive glass. It relies on the irreversible lightinduced radial birefringence in the bulk of the material. The ability of such birefringence pattern to convert the spin angular momentum of light into orbital optical angular momentum is exploited to demonstrate the production of large arrays of optical vortex generators with surface densities up to 104 cm−2

Nanostructuration par laser femtoseconde dans un verre photo-luminescent

L'objet de cette thèse est l'étude de l'interaction d'un laser femtoseconde avec un support photosensible particulier: un verre phosphate dopé à l'argent appelé verre photo-luminescent (PL). Une nouvelle approche permettant de réaliser en trois dimensions dans un verre PL des nanostructures d'argent aux dimensions bien inférieures à la limite de diffraction est tout d'abord présentée. La mesure des propriétés optiques et structurales pour différentes échelles (spatiales et temporelles) a permis de proposer un mécanisme de formation des structures photo-induites qui est basé sur un jeu subtil entre les phénomènes d absorption non-linéaire et de thermo-diffusion. La deuxième partie de cette thèse sera orientée sur les propriétés optiques (linéaires et non-linéaires) et les applications des ces nanostructures d argent. En particulier, l exaltation des propriétés non-linéaires des agrégats d argent sera exploitée pour stocker optiquement de l information en trois dimentions.The aim of this work is the study of the interaction between a femtosecond laser and a special photosensitive medium: a silver containing phosphate glass, also called photo-luminescent (PL) glass. A new approach allowing to write, inside the PL glass, 3D silver nanostructures with feature size down to the diffraction limit is presented. Based on optical and structural measurments at different time and spacial scales, the mechanism of the formation of these nanostructures is described. A subtle interplay between nonlinear absorption and thermo-diffusion effects is found to be the key of the mechanism. The second part of this work relies on the optical properties (linear and nonlinear) and few applications of the silver nanostructures. More particulary, the enhancement of their nonlinear properties is used for three dimentional optical data storage.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

HQBIT: Performing quantum optics practical work in a hybrid environment

Active learning based on experiments and practical work helps students understand concepts that challenge our conception of the physical world. However, such experiments can be hard to execute in a classroom context, due to their complexity, difficulty to set up and manipulate, and high cost. The development of digital materials dealt with some of these issues but also brought their own set of drawbacks and do not fulfill what a student is supposed to experience with a real experiment. To combine the advantages of both digital and physical approaches, we developed a hybrid optical bench based on numerical simulation, tangible manipulations, and pedagogical augmentations. In this paper, we present the design of the project and focus on two experimental scenarios