Molecular dynamics simulation of phase transitions in crystalline lead (II) fluoride

Using classical molecular dynamics applied to crystalline PbF2, we have simulated transitions between cubic and orthorhombic phases and reciprocally. These transitions were induced by pressure and temperature treatments. The orthorhombic phase was evidenced by analysis of different distribution functions and XRD spectra drawn from the ions positions in the simulated samples. (C) 2014 Elsevier B.V. All rights reserved

Studies of aluminum oxide thin films deposited by laser ablation technique

This paper presents the structural and optical investigations of the aluminum oxide nanocrystalline thin films. Investigated films were fabricated by laser ablation technique in high vacuum onto quartz substrates. The films were deposited at two different temperatures of the substrates equal to room temperature and 900 K. X-ray Diffraction spectra proved nanocrystalline character and the corundum phase of the film regardless on the substrate temperature during the deposition process. Values of the refractive indices, extinction and absorption coefficients were calculated by using Transmission and Reflection Spectroscopy in the UV–VIS–NIR range of the wavelength. Coupling Prism Method was used for films thickness estimations. Experimental measurements and theoretical calculations of the Third Harmonic Generation were also reported. Obtained results show that the lattice strain may affect obtained values of the third order nonlinear optical susceptibility

Functionalized azo-based iminopyridine rhenium complexes for nonlinear optical performance

Two new TTF-pi-acceptor dyads that contain p-nitrophenyl group as acceptor and bis-(styryl)benzene system as an efficient π−conjugated bridge have been synthesized by multistep synthetic procedure and their electrochemical behavior has been studied by cyclic voltammetry (CV). The occurrence of an intramolecular charge transfer (ICT) in these molecules has been evidenced by UV–Visible electronic absorption spectroscopy and these studies were completed by DFT calculations in both gas phase and in solution. The nonlinear optical parameters obtained via SHG and THG measurements are described and indicate that these materials are valuable candidates for the construction of optoelectronic and photonic devices. The Optical Kerr Effect measurements indicate that these materials exhibit a great potential in the field of optical switchers construction, where the material\u27s photoresponse time is a crucial parameter

Numerical simulation of rare earth ions clustering in silica by ion implantation

Date du colloque : 03/2010International audienc

Metal-induced efficient enhancement of nonlinear optical response in conjugated azo-based iminopyridine complexes

The nonlinear optical (NLO) properties of conjugated azo-based iminopyridine complexes with zinc and silver metal cations were studied. The processes of second and third harmonic generations in guest-host polymeric films were investigated and NLO parameters were extracted. Obtained second and third order NLO susceptibilities of zinc containing complex exceeds the latter of silver containing one. Using the Z-scan technique the NLO refractive index, NLO absorption coefficient, second order hyperpolarizability and NLO absorption cross section for the azo-based iminopyridine zinc (II) and silver (I) complexes were obtained and analyzed. Estimated nonlinearity/loss figure of merit of these complexes show promise for optical device applications

Simulation par dynamique moléculaire de la structure des verres dopés terre rare

National audienc

Picosecond third-order nonlinearity of lead-oxide glasses in the infrared

Heavy metal-oxide glasses containing lead and bismuth were prepared, and their picosecond third-order nonlinear (NL) optical characteristics were investigated. NL refractive indices of ≈ 10−18 m2/W at 1064 nm were measured. Negligible NL absorption was verified and, as a consequence, the samples present a good factor-of-merit for photonic applications

Investigation of the local environment of Eu3+ in a silicophosphate glass using site-selective spectroscopy and Molecular Dynamics simulations

Silicophosphate glasses (SiO2-P2O5) doped with Eu3+ ions were synthesized by the sol-gel process. Optical properties of these glasses were investigated by means of emission spectra and lifetime measurements. The Fluorescence Line Narrowing (FLN) technique was also used to explore the local structure around the Eu3+ ions in this host and to understand the role of phosphate as a codopant. As it is the case for aluminum, the ability of phosphate to avoid the rare earth clustering was investigated, and the role of this codopant in modifying the local order around the rare earth ion was evidenced. The analysis of the FLN spectra and lifetime measurements is consistent with this interpretation. Molecular Dynamics simulations were performed to evaluate and confirm these structural features. Two classes of europium sites were distinguished in agreement with the experimental characterization