Femtosecond Laser Structuring And Optical Properties Of A Silver And Zinc Phosphate Glass

We report on the micro- and nano-structuring of a silver-containing zinc phosphate glass under high repetition rate femtosecond near-infrared laser exposure. Luminescent silver clusters are locally formed thanks to multi-photon absorption. The excitation mechanisms in the glass are investigated with a transient absorption pump-probe experiment. The free electron density of the femtosecond-laser-induced ionized material for irradiation conditions leading to structural modifications is measured. We show that the involved photo-excitation process in the laser-glass interaction is a four-photon absorption and the measured free electron density is on the order of 10 17 cm- 3, four orders of magnitude below the critical electron density. The luminescence properties of these resulting structures have been investigated. Emission spectra are compared with those collected after different irradiations (γ and electron beams). The migration of silver species has been assigned to be responsible for local modifications and selective acid etching behavior of the structure. © 2010 Elsevier B.V. All rights reserved

Optical Properties of (C2H5C6H4NH2)2ZnBr2 Complex: Experimental and Quantum Chemical Studies

This study aims to develop a new type of semiconductor materials. In this context, the coordination complex (CH 3-CH 2-C 6 H 4-NH 2) 2 ZnBr 2 material was subjected to UV-Vis spectroscopy and the dependent theoretical density functional theory (TD-DFT) studies. The optical properties such optical absorption, band gap and molecular orbital energies are determined and discussed. The experimental results and theoretical conclusions appear to be in good agreement. Although we checked that the experimental molecular geometry is predicted correctly using the (TD-DFT) method. The molecular electrostatic potential (MEP) was calculated to predict physicochemical properties. The molecular composition of HOMO-LUMO and their band gap energies are represented in order to explain the activity of the title compound. So, the studied material seems to have a semiconductor behavior

The influence of potassium substitution for barium on the structure and property of silver-doped germano-gallate glasses

The structure and crystallization of silver-doped germano-gallate glasses for substitution of potassium for barium ions have been investigated. By means of Raman spectroscopy, a structural study has been carried out revealing a glass network depolymerization with the formation of non-bridging oxygens likely localized on germanium tetrahedra when the barium concentration increases. These structural modifications do not appear to significatively change the silver ion environments or ionic states, as reported on luminescence and optical transmission spectroscopies. A combined differential scanning calorimetry, X-ray diffraction characterization, scanning electron microscopy and micro-luminescence spectroscopy demonstrate that the barium ions introduction tends to stabilize the silver ions and to influence drastically the devitrification and the crystal growth kinetics. Correlations have been established between ionic conductivity, silver distribution and crystal growth mechanisms.ImPRession laser de fibres exOtiques Multi-MaTEriau

Influence Of Hydroxyl Group On Ir Transparency Of Tellurite-Based Glasses

A study of the glass properties with two opposite levels of hydroxyl content is presented for two different tellurite glass families with molar composition 70TeO2-10Bi2O3-20ZnO and 80TeO2-20Nb2O5. We show that melting tellurite-based glasses in a dried-oxidant atmosphere (relative humidity \u3c1%) reduces drastically the OH impurities. The effect of reducing the OH content on the glass properties such as characteristic temperatures, crystallization stability (ΔT), density, and microhardness is investigated. © 2013 The American Ceramic Society and Wiley Periodicals, Inc

Improvement of the photochromism taking place on ZnO/MoO3 combined material interfaces

Recently, we discovered a huge photochromic effect for ZnO/MoO 3 powder mixtures compared with the corresponding single oxides. The former study focused on the coloring efficiency after UV-light irradiation and demonstrated that the pre-existing electrons in the conductive band of ZnO are of huge importance to the photochromism efficiency. Herein, the creation of the ''self-closed Schottky barrier'' at the solid-solid interfaces between the two oxides, associated with the full redox reaction at the origin of the photochromic properties, was modulated by (i) doping ZnO with Al 3+ ions, (ii) annealing the powder mixture under low p(O 2) atmosphere, and (iii) synthesizing our own ZnO nanoparticles and MoO 3 particles using a polyol process. The characterization of the colouring effect under irradiation as well as the selfbleaching process allowed shedding light on this very complex photochromic mechanism. The coloring and bleaching efficiency (i.e. possibility to darken to more or less deep blue and to come back to the virgin material optical properties without any deterioration) depends upon multiple interconnected parameters controlling either the particle size and the interface areas between MoO 3 and ZnO oxides or the number of pre-electrons in conduction bands of ZnO and MoO 3 oxides. By correctly interpreting the ins and outs of the photochromism taking place at the created Schottky barriers in these binary ZnO/MoO 3 mixtures, the exchange of the electrons and the oxygen anions through this Schottky interface can be manipulated in order to optimize the huge photochromism phenomenon.Fluorures inorganiques photochrome

Investigation on the coloring and bleaching processes of WO3−x photochromic thin films

WO3−x (oxygen deficient tungsten oxide) thin films and WO3−x/Ta2O5 (tantalum oxide) composite films exhibit a huge photochromic effect with 60% near-infrared transmission modulation, in comparison to results in the literature. The colouring efficiency of such films results from both the stoichiometry of the particles (oxygen/tungsten deficient ratio) and the quality of the films (films are thin, homogeneous, and constituted of nanoparticles of about 5 nm in diameter and so with low scattering). Additionally, the high colouring efficiency obtained with a low fluence ultraviolet (UV) lamp is followed by a nearly complete bleaching phenomenon after a few hours in the dark. Beyond the attractiveness of our films toward multiple applications, and especially as films able to regulate the solar flow through smart windows, the optical properties and the colouring and bleaching kinetics were deeply investigated. For both the WO3−x thin films and the WO3−x/Ta2O5 composite films, colouring under irradiation and bleaching in the dark are phenomena that both proceed with a complex kinetics combining ultra-fast processes (from charge transfer, with a characteristic time of about one minute) and slower processes (linked to ionic diffusion, with a characteristic time of about one hour or even longer).ImPRession laser de fibres exOtiques Multi-MaTEriau

Effect of partial crystallization on the structural and Er3+ luminescence properties of phosphate-based glasses

In this paper, the impact of B2O3, ZnO and TiO2 addition on the structure, Er3+ luminescence and crystallization of glasses in the Er2O3single bondP2O5single bondCaOsingle bondSrOsingle bondNa2O glass system is reported. The thermal properties of the as-prepared glasses were recorded using a DTA and the structure of the glasses prior to and after heat treatment was analyzed using Raman and IR spectroscopies. Crystallization of the glass after heat treatments was confirmed by the presence of sharp peaks in the XRD patterns. Based on the XRD pattern, two different crystalline phases are suspected to precipitate, the composition of which depends on the glass composition. From the spectroscopic properties of the glasses, the Er3+ ions are not suspected to be incorporated in the crystals

Optical and structural characterization of femtosecond laser written micro-structures in germanate glass

Abstract We report on direct femtosecond laser writing in zinc barium gallo-germanate glasses. A combination of spectroscopic techniques allows to progress in the understanding of the mechanisms taking place depending on the energy. In the first regime (type I, isotropic local index change) up to 0.5 µJ, the main occurrence is the generation of charge traps inspected by luminescence, together with separation of charges detected by polarized second harmonic generation measurements. At higher pulse energies notably at the threshold corresponding to 0.8 µJ or in the second regime (type II modifications corresponding to nanograting formation energy domain), the main occurrence is a chemical change and re-organization of the network evidenced by the appearance of molecular O2 seen in the Raman spectra. In addition, the polarization dependence of the second harmonic generation in type II indicates that the organization of nanogratings may be perturbed by the laser-imprinted electric field

VO2 films obtained by V2O5 nanoparticle suspension reduction

International audienceApplications of vanadium dioxide, VO2 , able to modulate near-infrared radiation by changing from a transparent to a reflective/absorptive state, remain limited by its shaping as transparent films. In this work, a V 2 O 5 @PVP core-shell structure is designed prior to the formation of island-structured VO 2 films. Poly(N-vinyl-2-pyrrolidone) (PVP) is used as a surface stabilizer for the preparation of V2O5 NP suspensions; additionally, PVP acts as a reducing agent during the film post-annealing process, helping the V2O5 VO transformation under dynamic vacuum. Using in situ TG-FTIR characterization, the reducing mechanism is carefully discussed and analyzed. Finally, a uniform VO 2 film is fabricated with an attractive gray color and excellent thermal stability. Three strategies with various sintering parameters are used to optimize the film's morphology, i.e., surface coverage. In the last strategy, the thermochromic behavior of the designed island-structure VO2 film is simulated based on Mie scattering theory in consideration of surface coverage and "island" particle size fitting with our experiments. This pioneering work provides guidance for future studies on discontinuous VO 2 films

Laser Direct Writing of Silver Clusters‐Based Subwavelength Periodic Structures Embedded in Mid‐Infrared Gallo‐Germanate Glass

International audienceThe direct laser writing (DLW) using femtosecond lasers allows for the inscription of 3D microstructures embedded inside optical materials. Based solely on the silver ions photochemistry, the DLW in silver-containing glasses enables to locally induce inside glasses a unique combination of optical properties. The physical modifications of the material encompass not only a refractive index change, but also new physical properties like fluorescence, second- and third-harmonic generations, and surface plasmon resonance. Numerous efforts are deployed to develop the DLW-assisted silver photochemistry in phosphate glasses. However, this glass family is suffering from its near-infrared optical cutoff as opposed to the silver-doped gallo-germanate glasses. With an extended mid-infrared (mid-IR) transmission, these glasses are synthesized via the melt-quenching technique. Depending on the glass composition, either a glass matrix-based single track (Type I) or a silver cluster-based double track (Type A) of refractive index change is produced. By enabling an order of magnitude smaller structures than with Type I, Type A modification is further expanded to embed, for the first time, periodic structures below the inter-track spacing. Demonstrated with a pitch down to 400 nm, these Type A–based periodic structures bring new insights through the fabrication of 3D diffractive gratings in mid-IR glasses