Ce-doped LuAG single-crystal fibers grown from the melt for high-energy physics

n/

Spectroscopic properties of Er3+-doped antimony oxide glass

International audienceSpectroscopic properties of Er3+ ions have been studied in the 60Sb2O3-20WO3-19Na2O-1Bi2O3 (SWNB) glasses doped with 0.25 and 0.50 mol% Er2O3 respectively. The Judd-Ofelt parameters measured from the absorption spectra have been used to calculate the radiative life-time (τr) and the stimulated emission cross section. The low phonon energy, a reduced quenching effect and a high quantum efficiency of 90% for the 1.53 μm expected laser emission into pumping at 980 nm are in favor of promising material laser application

Photoluminescence Inhomogeneity of LGSO : Ce Scintillator Crystal

Spatial distribution of photoluminescence (PL) parameters in Lu2SiO5 : Ce (LSO : Ce) and Lu2xGd2 – 2xSiO5 : Ce (LGSO : Ce) are investigated using confocal microscopy. The PL spectra of both crys-tals are dominated by a single band peaked at 510 nm. A low intensity sub-band peaked at 600 nm is observed in LGSO:Ce. Spatial inhomogeneities down to submicron size are observed in spectral center of mass mapping images of LGSO : Ce while the spatial distributions of spectrally-integrated PL intensity and PL peak position showed no large variations. The inhomogeneities in LGSO : Ce are caused by the spectral variation of the long-wavelength sub-band and are attributed to Ce3+ located in CeO6 polyhedra. The results are explained by Lu / Gd ratio fluctuations in mixed LGSO : Ce crystals. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3526

Scattering defect in large diameter titanium-doped sapphire crystals grown by the Kyropoulos technique

International audienceThe Kyropoulos technique allows growing large diameter Ti doped sapphire for Chirped pulse amplification laser. A scattering defect peculiar to Kyropoulos grown crystals is presented. This defect is characterized by different techniques: luminescence, absorption measurement, X-ray rocking curve. The impact of this defect to the potential application in chirped pulse amplification CPA laser is evaluated. The nature of this defect is discussed. Modified convexity of the interface is proposed to avoid the formation of this defect and increase the quality of the Ti sapphire crystal

Ce-doped Li6Ln(BO3)3 (Ln = Y, Gd) Single crystals fibers grown by micro-pulling down method and luminescence properties

Ce3+-doped borate crystal fibers of Li6Gd(BO 3)3 (LGBO) and Li6Y(BO3)3 (LYBO) compositions are grown by the micro-pulling down (μ-PD) method for potential application in developing new neutron detectors. The ternary equilibrium diagram of Li2O-Gd2O3-B 2O3 is drawn and the preparations of homogeneous mixed LGBO and LYBO powders and growth conditions for single crystal fibers are discussed. Absorption, excitation and X-ray luminescence spectra are investigated. Absolute light yield derived from energy spectra and kinetic decay curves measured under α- and γ-scintillations of Ce 3+-doped LGBO and LYBO single crystal fibers is provided. © 2012 Elsevier B.V. All rights reserved

Recent progress on elaboration of undoped and doped Y2O3, Gd2O3 rare-earth nano-oxide

International audienc

Observation of Gas Bubble Incorporation during Micropulling-Down Growth of Sapphire.

International audienceQuite often sapphire shaped crystals contain specific defects called bubbles of average diameter higher than 100 mu m or microbubbles of diameter smaller than 10 mu m. These defects strongly affect the crystal properties. Bubbles of 100 mu m in diameter have been observed in the molten zone during micropulling-down of sapphire fibers. Before their incorporation inside the crystal, they show a periodic oscillation and consequently deform the crystallization interface. These observations are discussed with reference to the available literature

Drop model for continuous milli-beads production

International audienceProduction of solid spheres from droplet solidification is gaining more and more interest, but needs a careful control of the drop diameter. The technique of dropping liquid alumina from a nozzle is used for processing the starting materials which are filling the crucibles in sapphire crystal growth technology. In the present work, experimental, theoretical and numerical analysis is carried out in order to describe the time evolution of the drop formation from a capillary tube. The main goal of this study is to develop a physical model able to explain the dynamics of drop formation, with application in drop weight method and production of small alumina balls. A new formula predicting the volume of falling drops is derived from the force balance at the instant of drop detachment. The theoretical predictions are compared to present numerical computations and experimental results of alumina milli-beads production. Based on this model, the crucible and capillary tube geometries and the process parameters can be designed in order to get continuous production of reproducible droplets for mass production

Chemical Segregation of Titanium in Sapphire Single Crystals Grown by Micro-Pulling-Down Technique: Analytical Model and Experiments

International audienceThe micro-pulling-down (mu-PD) process consists in pulling a crystal under a capillary channel placed at the bottom of a crucible. Despite it being limited to rather small liquid volumes, it is used to grow single crystal fibers and shaped crystals of various cross sections, mainly applied industrially for optical applications, such as lasers, optics, or scintillators. Consequently, those crystals should be doped with active elements to fit the target application. Unfortunately, whatever the growth parameters and the dopant type, quite often segregation problems are observed. It is generally believed that chemical partition in mu-PD technique is restricted to the first grown millimeters, but some experiments show that it is not always the case. An analytical one-dimensional model is presented, aiming to predict the longitudinal segregation along the growth direction. It is shown that it depends in practice on growth parameters such as capillary length, meniscus height, capillary section, and pulling rate. The characteristic numbers controlling the segregation profile are derived and a parametric study is performed in the case of Ti-doped sapphire single crystal fibers. Ti3+:Al2O3 single crystal fibers oriented along c-axis have been grown under stationary stable growth regime using different pulling rates and the longitudinal chemical segregation has been characterized by photoluminescence. Results are in agreement with the model predictions