Effects of elevating temperature and high-temperature annealing upon state-of-the-art of yttia-alumino-silicate fibers doped with Bismuth

We report an experimental analysis of attenuation and fluorescence (at low-power 750-nm excitation) spectra' transformations in yttria-alumino-silicate fiber doped with Bismuth (Bi), which occur at higher than room, but not exceeding 700 degrees C, temperatures. As well, we address impact of elevating temperature upon the fiber's basic characteristics, such as fluorescence/resonant-absorption saturation, fluorescence lifetime, and pump-light backscattering, given by the presence of Bi-Al related active centers (BACs). The experimental data reveals dramatic impact of heating and high-temperature annealing in excess of 500...550 degrees C on the fiber's state-of-the-art, expressed as significant rise of resonant absorption, enhancement of BACs NIR fluorescence, and reduction of scattering loss. In the meantime, such microscopic parameters of the fiber as BACs fluorescence lifetime and saturation power are found to be kept almost unchanged in its post-annealed state as compared to the pristine one. Possible mechanisms responsible for the phenomena and advantages of utilizing temperature-treated fiber of such type for lasing/amplifying purposes are discussed. (C) 2016 Optical Society of Americ

КИНЕТИКА ПРОЦЕССА ОКИСЛИТЕЛЬНОГО ХЛОРИРОВАНИЯ МЕТАНА

Heterogeneous oxidative chlorination of methane was investigated. The target product is methyl chloride. The investigated terms and conditions of oxychlorination of methane: process temperature 400°C, pressure 0.1-0.9 MPa, catalyst (% weight.): copper chloride (II) 1-8%; potassium chloride 2.5%; lanthanum chloride 1%; carrier - aluminosilicate. Powder X-ray diffractometry and electron microscopy showed that the active catalyst components (CuCl2, KCl, LaCl3) are unevenly distributed on the support surface (α-Al2O3·SiO2) and form agglomerates with a high salt content, including binary chlorides such as KCuCl3, K2CuCl3 or K2CuCl4, hydrates K2CuCl4·2H2O and CuCl2·2H2O and hydroxychlorides Cu3Cl4(OH)2 and Cu2Cl(OH)3. The kinetics of methane oxychlorination was studied in a gradientless reactor at 400°C and pressure 0.1 - 0.9 MPa by varying the partial pressures of the reactants. Analysis of the products was carried out by GC. An equation of the reaction rate including partial pressures of methane, hydrogen chloride and water to the 0.77, 0.01 and 0.64 power, respectively, but of zero order by oxygen and chlorine provides an adequate description of methyl chloride formation rate. Significant influence of water partial pressure is proved for the reaction under consideration.Гетерогенно-каталитическая реакция окислительного хлорирования метана, целевым продуктом которой является хлористый метил, изучена при температуре 400°С и варьировании давления в диапазоне 0.1-0.9 МПа. Методами дифрактометрии и электронной микроскопии показано, что активные компоненты катализатора (CuCl2, KCl, LaCl3) распределяются неравномерно на поверхности носителя (α-Al2O3·SiO2), образуя агломераты с повышенным содержанием солей, в том числе двойных хлоридов, таких как KCuCl3, K2CuCl3 или K2CuCl4, гидрата K2CuCl4·2H2O и гидроксихлоридов состава Cu3Cl4(OH)2 и Cu2Cl(OH)3. Кинетические закономерности изучены в проточном безградиентном по парциальным давлениям реакторе при 400°С методом однофакторного эксперимента при варьировании парциальных давлений реагентов. Анализ продуктов проводили методом газовой хроматографии. Обработкой кинетических данных степенными уравнениями показано, что адекватное описание скорости образования хлористого метила обеспечивает уравнение, в которое входят парциальные давления метана, хлористого водорода и воды в степенях 0.77, 0.01 и 0.64, соответственно, при нулевых порядках по кислороду и хлору

On the structure of phosphosilicate glasses

Abstract Vibrational spectra of phosphosilicate glasses with P 2 O 5 concentrations up to 15 mol% are investigated by the methods of Raman spectroscopy and quantum-chemical modeling. We have found that the Raman band at 1320 cm À1 characteristic for such glasses is not simple and may be decomposed into two components with frequencies at %1317 and %1330 cm À1 caused in our opinion by single phosphorus centers (O@PO 3 tetrahedra surrounded by SiO 4 ones) and by double phosphorus centers (pairs of O@PO 3 tetrahedra bonded by a common oxygen atom). In the investigated phosphosilicate glasses manufactured by MCVD and SPCVD methods the ratio of concentrations of single and double centers varies from 1:5 to 1:2. A novel interpretation of the Raman bands distinct from the traditional one is suggested. The approach to the Raman spectra analysis developed in this article can be applied for control and optimization of manufacturing process of phosphosilicate and similar glasses as well as optical fibers

Stimulated Raman scattering in natural crystals of SrSO4, BaSO4 and PbSO4: High-order Stokes and anti-Stokes generation with single-wavelength UV, visible, and near-IR excitation, as well as cascaded up-conversion nonlinear chi ((3)) <-> chi ((3)) lasing effects under dual-wavelength picosecond collinear coherent pumping

Orthorhombic crystals of SrSO4, BaSO4, and PbSO4, known as natural crystals celestine, barite, and anglesite, were found to be attractive chi ((3))-active nonlinear optical materials. High-order Stokes and anti-Stokes picosecond generation that spans almost two octaves has been recorded with single-wavelength laser excitation in the UV, visible, and near-IR ranges. All recorded Raman induced lasing components were identified and attributed to the SRS-promoting vibration modes of the studied crystals (omega (SRS)a parts per thousand 999 cm(-1) for SrSO4,omega (SRS)a parts per thousand 985 cm(-1) for BaSO4 and omega (SRS)a parts per thousand 977 cm(-1) for PbSO4). Under dual-wavelength (lambda (f1)=1.06415 mu m + lambda (f2)=0.53207 mu m) collinear coherent picosecond pumping several new manifestations of cascaded chi ((3)) chi ((3)) nonlinear up-conversion lasing effects were observed in BaSO4 and SrSO4 crystals. We classify all three studied sulfate crystals as promising SRS-active materials for Raman laser frequency converters and as efficient chi ((3))-crystals that efficiently generate Stokes and anti-Stokes frequency combs, which can enable experiments of ultra-short pulse syntheses

Low-frequency dynamics of glasses and crystals of similar compositions

Wide range (10–1500 cm-1) dielectric and Raman spectra of crystals and glasses of similar compositions were analysed with the use of both literature (a-quartz, cristobalite, LaBGeO5, Pb5Ge3O11, As2Se3, etc.) and original (Li2Ge7O15, LiBaPO4) data. For all structural types (island, chain, layer or frame like), the boson peak (BP)in the glass spectrum (GS) corresponds to one or several bands in the low frequency (LF) spectrum of the corresponding crystal. In this sense, the LF range (<200 cm-1) is not a specific feature of GS as compared to higher frequency range of stretching and bending modes, where the crystal spectral bands are widened due to disordering and/or vitrification up to their full conversion into a diffuse GS. Therefore the origin of LF bands in GS can be identified taking into account the nature of corresponding bonds in the crystal spectrum by analogy with well known procedure of interpretation of stretching and bending vibrations in GS. The approach proposed is exemplified by different systems. Lead germanate glasses reveal several highly overlapping LF peaks, which originate from optical vibrations of lead atoms by analogy with Pb5Ge3O11 crystal spectrum. The Li2Ge7O15 glass and crystal LF peaks correspond to vibrations of oxygen in layer fragments of the structure. Cristobalite-like structure of silica glass is proposed on the assumption of coincidence of peak frequencies in their Raman spectra at ~50 cm-1, whereas a-quartz has no vibrational modes below 100 cm-1. Thus, the approach proposed allows one to refine and concretise the universal nature of the BP, referring to the short and medium range structure and the vibrational properties of the corresponding crystal

More than two-octaves span of the Stokes and anti-Stokes picosecond lasing comb in orthorhombic natural single crystals of celestine, SrSO4

Efficient room-temperature Stokes and anti-Stokes chi((3))-nonlinear picosecond generation, which spans more than two octaves (approximate to 23012 cm(-1)) has been observed in a natural crystal of orthorhombic SrSO4 (celestine). All recorded lasing lines in the visible and near-IR regions are identified and attributed to its SRS-promoting vibration mode omega(SRS) approximate to 999 cm(-1). [GRAPHICS] (C) 2010 by Astro Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGa

KINETICS OF OXIDATIVE CHLORINATION OF METHANE

Heterogeneous oxidative chlorination of methane was investigated. The target product is methyl chloride. The investigated terms and conditions of oxychlorination of methane: process temperature 400°C, pressure 0.1-0.9 MPa, catalyst (% weight.): copper chloride (II) 1-8%; potassium chloride 2.5%; lanthanum chloride 1%; carrier - aluminosilicate. Powder X-ray diffractometry and electron microscopy showed that the active catalyst components (CuCl2, KCl, LaCl3) are unevenly distributed on the support surface (α-Al2O3·SiO2) and form agglomerates with a high salt content, including binary chlorides such as KCuCl3, K2CuCl3 or K2CuCl4, hydrates K2CuCl4·2H2O and CuCl2·2H2O and hydroxychlorides Cu3Cl4(OH)2 and Cu2Cl(OH)3. The kinetics of methane oxychlorination was studied in a gradientless reactor at 400°C and pressure 0.1 - 0.9 MPa by varying the partial pressures of the reactants. Analysis of the products was carried out by GC. An equation of the reaction rate including partial pressures of methane, hydrogen chloride and water to the 0.77, 0.01 and 0.64 power, respectively, but of zero order by oxygen and chlorine provides an adequate description of methyl chloride formation rate. Significant influence of water partial pressure is proved for the reaction under consideration

Basic and Peculiar Properties of Chromium-Magnesium Co-Doped YAS-Based Optical Fibers

The basic and peculiar properties of new-type chromium (Cr) and magnesium (Mg) co-doped yttrio-alumino-silicate-based optical fibers, fabricated through the classic modified chemical vapor deposition method employed in conjunction with solution-doping technique, are addressed, with most of attention being paid to impact of Cr/Mg co-doping strength. The electron probe microanalysis, Raman, optical absorption, and fluorescence at excitation at different wavelengths, spanning visible to near-infrared (NIR)] spectra' measurements are performed for clarifying overall state-of-the-art of the fibers. Their most remarkable features are demonstrated to be pronounceable fluorescence in NIR (beyond 1 mu m) and as well pronounceable bleaching effect under the action of 1-mu m light, both adherent to the presence of Cr4+ ions