A. Monteil
University of Angers
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Featured researches published by A. Monteil.
Optical Materials | 2003
Raffaella Rolli; M. Montagna; Stéphane Chaussedent; A. Monteil; Victor K. Tikhomirov; M. Ferrari
Optical transitions of Er 3þ ion in two tellurite glasses of molar composition 75TeO2:12ZnO:10Na2O:2PbO:1Er2O3 and 75TeO2:12ZnO:10Na2O:2GeO2:1Er2O3 were investigated. The measured absorption and emission spectra were analysed by Judd–Ofelt and McCumber theories, in order to obtain radiative transition rates and stimulated emission cross sections. It was found that these glasses have high and broadband absorption and stimulated emission cross sections at 1.5 lm. For the metastable 4 I13=2 level, by comparing the measured lifetime with the calculated radiative decay time, quantum efficiency higher than 80% was found.
Journal of Non-crystalline Solids | 1999
C. Armellini; M. Ferrari; M. Montagna; Georg Pucker; Christope Bernard; A. Monteil
Monolithic silica xerogels doped with diAerent concentrations of Tb 3a and Al 3a (xTbO1:5‐x6AlO1:5‐SiO2, xa 2 · 10 ˇ4 ,4 ·10 ˇ4 ,5 ·10 ˇ3 ) were prepared by a sol‐gel route: Mixtures of tetra-methoxy-silane, Tb(NO3)3 AE 5H2O, Al(NO3)3 AE 9H2O, ethanol, and water were condensed at 60∞C using HNO3 as catalyst. The samples were sintered at 950∞C for 86 h in air. The Raman spectra indicate several structural diAerences among the samples and show that there is a compositional dependence of the gel glass transformation temperature. The sample with xa 5 · 10 ˇ3 is glasslike on the outer part showing onset of crystallisation in the inner part of the sample. The samples with smallest dopant concentrations (xa 2 · 10 ˇ4 ,4 ·10 ˇ4 ) contain pores. All samples luminesce from the 5 D4 and 5 D3 states of Tb 3a with excitation at 355 nm. The 5 D3 luminescence increases with respect to the 5 D4 luminescence with increasing dopant concentration, indicating that the larger Al 3a concentrations are eAective in dispersing Tb 3a ions. This result is also confirmed by the analysis of the decay of the 5 D3 and 5 D4 luminescence. ” 1999 Elsevier Science B.V. All rights reserved.
Journal of Sol-Gel Science and Technology | 2003
L. Zampedri; M. Ferrari; C. Armellini; F. Visintainer; C. Tosello; Sabina Ronchin; Raffaella Rolli; M. Montagna; A. Chiasera; S. Pelli; Giancarlo C. Righini; A. Monteil; C. Duverger; Rogéria Rocha Gonçalves
Abstract(100 − x)SiO2-(x)TiO2-ErO3/2 planar waveguides, with 7 ≤ x ≤ 20 have been prepared by sol-gel route using the dip-coating technique. The thickness of the films was optimized to support a single propagating mode at 1550 nm, with a confinement coefficient higher than 0.75. The process of densification of the gel and the devitrification with the growth of TiO2 nanocrystals were studied by Raman scattering. Devitrification is important only for x ≥ 15, but it was not possible to obtain full densification of the samples, even at the lowest TiO2 content, without the appearance of nanocrystals.Emission in the C telecom band was observed; the spectral width of the 4I13/2 → 4I15/2 transition of Er3+ slightly increases with the titania content. For x ≤ 12 most of Er3+ ions (about 65%) decay exponentially with a lifetime of about 8 ms.
Optical Materials | 2004
Johann Troles; F. Smektala; Georges Boudebs; A. Monteil; Bruno Bureau; Jacques Lucas
Abstract Chalcogenide glasses present high values for third-order non-linear optical properties, i.e., high non-linear refractive indices (800 times as high as the non-linearity of silica glass at 1.064 μm) and a high non-linear absorption coefficient, which can reach more than 5 cm/GW. We study here the optical limiting properties of several chalcogenide glasses at 1.064 μm with a picosecond pulsed Nd:YAG laser and we observed a real optical limiting behavior. In the case of GeAs2Se2, glass for example, the decrease of the transmitted intensity is around 75% compared to the theoretical linear transmission, for incident pulses of 5 GW/cm2. The comparison between the theoretical non-linear transmission induced by the two photon absorption effect and the experimental non-linear transmittance shows that the optical limiting properties are mainly due to non-linear absorption.
Journal of The Optical Society of America B-optical Physics | 2004
Sudhir Cherukulappurath; Georges Boudebs; A. Monteil
We present a powerful but simple technique based on a 4f coherent imager system with top-hat beams to characterize nonlinear optical properties. We describe the theoretical model and the experimental details of the measurement for materials having nonlinear refraction with or without nonlinear absorption. We show that it is possible to characterize the nonlinearities by analyzing the intensity profile of the image after nonlinear filtering through the material placed in the Fourier plane of the setup. We will show that, as in the Z-scan technique, the use of top-hat beams instead of Gaussian beams increases the sensitivity of the measurement. Intensity-dependent nonlinearities can be studied by use of this single laser-shot technique. We validate this nonlinear imaging technique by measuring the absolute value of the n2 coefficient for CS2 and some well-known chalcogenide glasses (As2S3, As2Se3, GeSe4, and Ge10As10Se80). Our values are in good agreement with those obtained by other techniques.
Optical Materials | 2003
Johann Troles; F. Smektala; Georges Boudebs; A. Monteil
Abstract The vitreous formation in a new chalcohalogenide system based on As, Sb, Bi, S, Pb and I has been studied. Wide vitreous regions have been identified both in the ternary As 2 S 3 –Sb 2 S 3 –PbI 2 system and in the quaternary As 2 S 3 –Sb 2 S 3 –Bi 2 S 3 –PbI 2 system. More particularly, in the latter case, the vitreous regions have been investigated and established for the two layers of the system corresponding respectively to 10% and 20% molar of Bi 2 S 3 . Due to the richness of these new glasses in highly polarizable elements, they are of interest for the implementation of high nonlinear optical properties. To explore the potentialities of chalcogenide glasses for ultra-fast optical applications, the nonlinear refractive indices (real and imaginary part) of different compositions are measured. Nonlinear measurements have been performed through a pump/probe experiment using a Mach-Zehnder interferometer coupled to a CCD camera. The measured values are as high as 16×10 −18 m 2 /W for the nonlinear refractive index and 6 cm/GW for the nonlinear absorption.
Journal of Non-crystalline Solids | 2003
A. Kerrache; Victor Teboul; D. Guichaoua; A. Monteil
Abstract Using molecular dynamics simulations we investigate the presence of dynamical heterogeneities in supercooled silica, a ‘strong’ glass former, and the changes as a function of time of these heterogeneities during aging. We compare the radial distribution functions for the 10% most mobile silicon or oxygen atoms with the corresponding mean radial distribution functions. We measure changes of these radial distribution functions and the changes of the non-gaussian parameters with time after a quench. We find that dynamical heterogeneities are present in silica and that they increase during the aging process. We find that the oxygen and silicon atoms show similar heterogeneities but with a differing rate of change during aging.
Journal of Chemical Physics | 1996
Stéphane Chaussedent; A. Monteil
As a prelude to a spectroscopic investigation of doped wet gels, we have made molecular dynamics simulations of a very dilute EuCl3 solution. The symmetry properties of the first hydration shell of Eu3+ have been determined. The 8 water molecules of this shell are roughly arranged according to the square antiprism D4d pseudo‐symmetry. Though the arrangement of oxygens is little distorted from regular positions, the orientation of the water molecules themselves is found to be not so well organized at room temperature.
Journal of Non-crystalline Solids | 2001
Christope Bernard; Stéphane Chaussedent; A. Monteil; Nathalie Balu; Jacques Obriot; C. Duverger; M. Ferrari; M. Bouazaoui; C. Kinowski; S. Turrell
In this paper, we report on the results obtained from molecular dynamic simulation of a Eu3+-doped germanosilicate glass. This simulation provides further information on the structure. In particular it reveals a homogeneous distribution of SiO4 and GeO4 units, a decrease of defects compared to SiO2 and GeO2 glasses, and a trend to clustering of the doping ions. Using the modified crystal-field theory, the luminescence spectroscopic properties have been computed and comparison with experimental data has allowed a correlation of the spectral features with two main types of local environment depending on the coordination number and on the medium-range arrangement around the doping ions.
Current Opinion in Solid State & Materials Science | 2003
Stéphane Chaussedent; Victor Teboul; A. Monteil
In the recent years the use of the molecular dynamics technique has become very common in the study of glass. The purpose of the present paper is to focus on recent advancements on the use of this method to investigate rare-earth-doped glasses. We report an overview of the use of simulations to study their specific structural features and luminescence properties.