Ultrafast nonlinearity of antimony polyphosphate glasses

We report on the ultrafast nonlinearity of antimony polyphosphate glasses measured using the Kerr shutter technique. The nonlinear refractive index, n(2), was (1.1+/-0.2)x10(-14) cm(2)/W at 800 nm, and enhancement of n(2) by approximate to80% was observed by adding 10% of lead oxide in the glass composition. The full width at half-maximum of the third-order correlation signal was 150 fs, which implies a fast response of the samples (less than or equal to100 fs). Nonlinear absorption was negligible in the range of intensities used. (C) 2003 American Institute of Physics.

Reversible holographic glasses using visible lasers

Antimony based glasses have been investigated for the first time regarding the possibility of holographic data storage using visible lasers sources. Changes in both refractive index and the absorption coefficient were measured using a holographic setup. The modulation of the optical constants is reversible by heat treatment. Bragg gratings were written under visible light of an Ar laser and erased thermally.

Comparison of metallic and ceramic tubes as atomization cells for tin determination by TS-FF-AAS

This work describes the development of an analytical procedure for on-line tin determination using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). Two tubes were evaluated as atomization cells: a metallic tube (Ni-Cr, principal components composition: 73.95% Ni and 16.05% Cr) and a ceramic tube (99.8% Al2O3). The use of air as the carrier was made by employing a Rheodyne valve to inject the samples, allowing an analytical frequency of 90 h(-1) and avoiding sample dispersion. The carrier flow rate (air), sample volume injected, and acid concentration (HCl) were evaluated for the optimization of the TS-FF-AAS system. The sensitivity for 50 mL of analytical solution with TS-FF-AAS was 2 and 5 times higher (to metallic and ceramic tube, respectively) than using an acetylene-nitrous oxide flame with pneumatic aspiration (requiring a sample volume of approximately 20 times higher.

Twentyfold blue upconversion emission enhancement through thermal effects in Pr3+/Yb3+-codoped fluoroindate glasses excited at 1.064 mu m

Infrared-to-visible upconversion emission enhancement through thermal effects in Yb3+-sensitized Pr3+-doped fluoroindate glasses excited at 1.064 mu m is investigated. A twentyfold increase in the 485 nm blue emission intensity as the sample temperature was varied from 20 to 260 degrees C was observed. The visible upconversion fluorescence enhancement is ascribed to the temperature dependent multiphonon-assisted anti-Stokes excitation of the ytterbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature dependent effective absorption cross section for the F-2(7/2)-->F-2(5/2) transition of the Yb3+ and (1)G(4)-->P-3(0) excited-state absorption of the Pr3+, agrees very well with the experimental results. (C) 2000 American Institute of Physics. [S0021-8979(00)08209-8].

Photosensitivity in antimony based glasses

New glass forming systems based on Sb2O3-SbPO4 has been explored. These glasses present higher thermal stability against devitrification and higher refractive index than chalcogenide glasses. Under irradiation, using Ar-laser 350nm wavelength and 50 mW power density, change on the coloration is observed. Structural and electronic modifications around Sb cations induced by such treatment have been characterized by XANES measurements at the L-Sb edges. on the one hand, XANES spectra, at the LJ edge, show a decrease of the coordination number for Sb atoms induced by exposure to light indicating a breaking of Sb-O bonds in the glassy network. on the other hand, XANES spectra, at the Lt edge, suggest a change in the oxidation state of Sb atoms. These modifications associated to the photodarkening of the glass is reversible either after a couple of days or after heating the glass at the glass transition temperature, T-g.

Scandium fluorophosphate glasses: a structural approach

A systematic investigation on glass formation in the ternary system InF3-BaF2-[Sc(PO3)(3)](n) has been carried out. Scandium polyphosphate [Sc(PO3)(3)](n) has been used as a third component in order to investigate the possibilities of obtaining new stable glasses. The above long-chain polyphosphate has been prepared using a specially elaborated cryo-technique, which allowed the preparation of high-purity product. Stable ternary compositions have been obtained within the compositions range (in mol%): 5-75 InF3, 0-80% BaF2, 0-50% [Sc(PO3)(3)](n). Glasses were characterized by Differential Scanning Calorimetry, vibrational spectroscopy (Raman) and P-31 NMR. Structural features for the glass were put forward. Isolated P(O,F)4 groups or fluoroindated metaphosphate units could be identified depending on glass compositions. (C) 2002 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

Red-green-blue upconversion emission and energy-transfer between Tm3+ and Er3+ ions in tellurite glasses excited at 1.064 mu m

Red, green, and blue emission through frequency upconversion and energy-transfer processes in tellurite glasses doped with Tm3+ and Er3+ excited at 1.064 mum is investigated. The Tm3+/Er3+-codoped samples produced intense upconversion emission signals at around 480, 530, 550 and 660 nm. The 480 nm blue emission was originated from the (1)G(4)-->H-3(6) transition of the Tm3+ ions excited by a multiphoton stepwise phonon-assisted excited-state absorption process. The 5 30, 5 50 nm green and 660 mn red upconversion luminescences were identified as originating from the H-2(11/2), S-4(3/2) --> I-4(15/2) and F-4(9/2) --> I-4(15/2) transitions of the Er3+ ions, respectively, populated via efficient cross-relaxation processes and excited-state absorption. White light generation employing a single infrared excitation source is also examined. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Glasses containing lutetium fluoride

Glasses containing lutetium fluoride have been prepared in the system BaF2 - SrF2 - ZnF2 - LuF3 - InF3. The composition of the phases crystalling out of these glasses suggests octahedral pre-arrangement comprising [LuF6] and [Sr(Ba)F-2 structural fragments.

Antimony orthophosphate glasses with large nonlinear refractive indices, low two-photon absorption coefficients, and ultrafast response

Antimony glasses based on the composition Sb2O3-SbPO4 were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n(2), of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n(2) was observed by adding lead oxide to the Sb2O3-SbPO4 composition. Large values of n(2)approximate to10(-14) cm(2)/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications. (C) 2005 American Institute of Physics.

Raman investigation of structural photoinduced irreversible changes of Ga10Ge25S65 chalcogenide glasses

The influence of time exposure, when exposed to above band gap light (3,52 eV) and annealing, on Ga10Ge25S65 glasses has been studied through their effects on the structure and optical properties. To evaluate the photostructural change infrared and Raman spectra for bulk Ga10Ge25S65 glasses have been measured before and after exposure. The Raman spectra are interpreted in terms of models in which the Ge atoms are fourfold coordinated and the S atoms are two fold coordinated. The observed changes in the spectral region of (S-S) stretching vibration (470-490 cm (-1)) is a direct evidence for the occurrence of important structural changes in local bonding configuration caused by optical irradiation. It is shown that the dominant photostrucural changes are chain formation tendency of the chalcogenide atoms under the laser irradiation rather than rings.

Synthesis and structural investigations on TeO2-PbF2-CdF2 glasses and transparent glass-ceramics

New glasses have been prepared in the oxifluoride mixed system TeO2-PbF2-CdF2. Starting from pure TeO2 the addition of the fluorides leads to a decrease in the glasses characteristic temperatures. Also from Raman scattering results a structural evolution was observed where the number of structural units described as [TeO3] trigonal pyramids and [TeO3+1] polyhedra increases at the expense of the [TeO4] trigonal bipyramids supposed to exist in the TeO2, rich samples. Transparent glass ceramics were obtained from the glass with composition 80TeO(2)-10PbF(2)-10CdF(2), (mol%) with the PbTe3O7 crystalline phase being identified by X-ray diffraction and EXAFS measurements performed at the Te K, Cd K and Pb L-III edges. Also from Exafs measurements it is proposed that cadmium ions are preferentially surrounded by oxygen atoms although they were in a fluoride anion environment in the starting material. (C) 2002 Published by Elsevier B.V. Ltd.

Lead-cadmium oxyfluoride glasses and glass-ceramics

Glasses and glass-ceramics have been obtained in oxyfluoride systems involving lead and cadmium fluorides and one of the well-known glass former oxides SiO2, B2O3 and TeO2. Vitreous domains were established and a wide range of compositions including high heavy metal contents lead to stable glasses. Amorphous structures have been studied by short-range order spectroscopy techniques (Raman scattering and x-ray absorption) and molecular basic structures have been identified. Besides the usual oxides, the role of glass former could also be proposed for cadmium ions. Special attention has been paid for crystallization process. Cubic lead fluoride, cubic lead tellurite, tetragonal tellurium oxide and a solid solution of the type Pb1-xCdxF2 are obtained as crystallization products depending on the composition and temperature of heat treatments. Pb1-xCdxF2 solid solutions are well known superionic materials and obtaining this solid solution as a crystal phase could be very interesting for applications concerning ionic electrical conduction properties. The addition of rare earth ions led to the control of the crystallization process. In the presence of the nucleating ion only the cubic form beta-PbF2 was identified. Rare earth ions are present in the crystal phase and crystal-like spectroscopic properties were observed suggesting interesting applications for these perfectly transparent glass ceramics in photonics.

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited at 1540 nm

Temperature investigation of infrared-to-visible frequency upconversion in erbium-doped tellurite glasses excited by CW laser radiation at 1540 nm and under cryogenic temperatures is reported. Intense upconversion emission signals around 530, 550 and 660 nm corresponding to the H-2(11/2), S-4(3/2), and F-4(9/2) transitions to the I-4(15/2) ground state were generated and studied as a function of the laser intensity and temperature. The upconversion excitation mechanism of the Er3+ ions emitting energy levels was accomplished via stepwise multiphoton absorption. The green upconversion luminescence exhibited a fivefold intensity enhancement when the temperature of the sample was varied in the range between 5 and 300 K. A maximum green upconversion intensity was attained around 120 K and a steady decreasing behavior for higher temperatures up to 300 K was observed. A model based upon conventional rate equations was used to model the observed temperature evolution of the upconversion luminescence. (C) 2002 Elsevier B.V. B.V. All rights reserved.

BaTiO3 obtained through metallic stearate precursors

Metallic stearates were used as precursors to obtain BaTiO3. Barium and titanium stearate mixtures were homogenized in ball mill containing some amount of ammonium stearate. The mixture of the precursors was evaluated by simultaneous TG/ DTA and TMA, and residues from thermal decomposition were characterized by XRD and SEM. It could be verified that the residues from the thermal decomposition in both oxidant and inert atmospheres were the BaTiO3 but with characteristic morphological and crystalline aspects depending on the experimental conditions in which the mixtures of precursors were obtained. (C) 2002 Elsevier B.V. B.V. All rights reserved.