Search results for "Optica"

Higher-order Kerr terms allow ionization-free filamentation in gases

2010

Talk given by J. Kasparian; International audience; Higher-order nonlinear indices, rather than plasma, provide the main defocusing contribution to filamentation in gases at 800 nm. Developing generalized Miller formulae, we discuss the generality of this as a function of the laser wavelength

Alignment of linear molecules by short duration laser pulses

2005

Alignment of linear molecules is efficiently induced by strong linearly polarized laser pulses. In the case of short pulses with respect to molecular rotation, periodic alignment appears in field-free conditions after the extinction of the field. This manuscript presents three techniques where the value of allows to quantify alignment without molecular dissociation nor additional alignment. They use a weak time-delayed probe pulse which experiences the optical properties of an aligned sample and shows modification of its characteristics. The first of them measures a depolarization due to the birefringence of the sample. The second one is based on the defocusing produced by the spatial distr…

Copper Induces a Core Plasmon in Intermetallic Au(144,145)–xCux(SR)60 Nanoclusters

2015

The electronic structure and optical absorption spectra of intermetallic thiol-stabilized gold-copper clusters, having 144-145 metal atoms and 60 thiols, were studied by ab initio computations. The widely known icosahedral-based cluster model from the work of Lopez-Acevedo et al. (2009) was used, and clusters doped with one to 30 copper atoms were considered. When doped inside the metal core, copper induces dramatic changes in the optical spectrum as compared to the previously studied all-gold Au144(SR)60. An intense broad absorption peak develops in the range 535-587 nm depending on the amount of doping and doping sites. This result agrees very well with recent experiments by the Dass grou…

Single Crystal Sub‐Nanometer Sized Cu6(SR)6 Clusters: Structure, Photophysical Properties, and Electrochemical Sensing

2016

Organic ligand-protected metal nanoclusters have attracted extensively attention owing to their atomically precise composition, determined atom-packing structure and the fascinating properties and promising applications. To date, most research has been focused on thiol-stabilized gold and silver nanoclusters and their single crystal structures. Here the single crystal copper nanocluster species (Cu6(SC7H4NO)6) determined by X-ray crystallography and mass spectrometry is presented. The hexanuclear copper core is a distorted octahedron surrounded by six mercaptobenzoxazole ligands as protecting units through a simple bridging bonding motif. Density functional theory (DFT) calculations provide…

Optical Absorption of Excimer Laser‐Induced Dichlorine Monoxide in Silica Glass and Excitation of Singlet Oxygen Luminescence by Energy Transfer from…

2021

An optical absorption (OA) band of interstitial dichlorine monoxide molecules with peak at 4.7 eV and halfwidth 0.94 eV is identified in F2 laser - irradiated (photon energy=7.9 eV) synthetic silica glass bearing both interstitial O2 and Cl2 molecules. Alongside with intrinsic defects, this OA band can contribute to solarization of silica glasses produced from SiCl4. While the formation of ClClO is confirmed by its Raman signature, its structural isomer ClOCl may also contribute to this induced OA band. Thermal destruction of this band between 300C and 400C almost completely restores the pre-irradiation concentration of interstitial Cl2. An additional weak OA band at 3.5 eV is tentatively a…

Choroidal thickness and morphology analysed by optical coherence tomography as a method to approach diabetic ocular disease prognosis and progression

2019

TÍTULO ESPESOR COROIDEO Y MORFOLOGÍA ANALIZADO POR TOMOGRAFÍA DE COHERENCIA ÓPTICA COMO MÉTODO PARA ABORDAR LA PROGNOSIS Y LA PROGRESIÓN DE LA ENFERMEDAD OCULAR DIABÉTICA INTRODUCCIÓN La evidencia clínica in vivo de coroidopatía diabética (DC) ha sido difícil de demostrar clínicamente debido a la falta de medios para visualizar la coroides. Los avances de la tecnología de la tomografía de coherencia óptica (OCT) permitieron la visualización in vivo de la coroides. Los resultados controvertidos en la Diabetes para el grosor coroideo (CT) y la falta de identificación de los cambios morfológicos hacen que la DC identificada con OCT aún no se conozca. PROPÓSITO Evaluar si la medición por CT sol…

Radiation effects on antimonium-doped Yb-fibers

2013

Etude spectroscopique de fibres durcies pour un environnement radiatif sévère

2013

Les nouveaux environnements radiatifs, comme LMJ, ITER, ILE/ELI, HiPER, réacteurs nucléaires des générations III+ et IV, nécessitent le développement de nouveaux composants pour le transport et le traitement des signaux. A cause de l’impossibilité d’utiliser les composants électroniques, la recherche est orientée vers les composants à fibres optiques comme vecteur d’information et aussi comme élément de diagnostic. Ils présentent de nombreux avantages, comme leur relative immunité électromagnétique, faible pois, large bande passante, mais les rayonnements gamma et les neutrons dégradent leur transmission. La dégradation dépend principalement de la composition de la fibre. Ainsi, il a été mo…

Conic optical fiber probe for generation and characterization of microbubbles in liquids

2021

A novel optical fiber probe has been developed to provide mechanical stability to microbubbles generated in fluids, the tip of the fiber is etched with hydrofluoric acid to pierce a truncated horn that fastens the microbubbles to the fiber tip and prevents misalignment or detachment caused by convection currents, vibrations or shocks in the liquid. Microbubbles are photo-thermally generated on the etched fiber and used as Fabry-Perot cavity sensor. Two methods were used to interrogate the probe: the first one, in the wavelength domain, is suitable for calibration in static or quasi static situations; the second one, in the time domain, can be used in dynamic environments. Experimental resul…

Radioluminescence Response of Ce-, Cu-, and Gd-Doped Silica Glasses for Dosimetry of Pulsed Electron Beams

2021

Radiation-induced emission of doped sol-gel silica glass samples was investigated under a pulsed 20-MeV electron beam. The studied samples were drawn rods doped with cerium, copper, or gadolinium ions, which were connected to multimode pure-silica core fibers to transport the induced luminescence from the irradiation area to a signal readout system. The luminescence pulses in the samples induced by the electron bunches were studied as a function of deposited dose per electron bunch. All the investigated samples were found to have a linear response in terms of luminescence as a function of electron bunch sizes between 10−5 Gy/bunch and 1.5×10−2 Gy/bunch. The presented results show that these…