Guillaume Guery

A new multimodal approach that combines linear and nonlinear vibrational spectroscopies and hyper Rayleigh scattering has been applied in the TeO2–TaO5/2–ZnO glass system to assess and quantify the relation between Raman gain and optical responses within the glass’ network arrangement. The level of polymerization of the TeO4 chain-like structure in a TeO2 glass system has been identified to be the main parameter for reaching high linear and nonlinear optical constant. We have observed that… Voir plus

A new multimodal approach that combines linear and nonlinear vibrational spectroscopies and hyper Rayleigh scattering has been applied in the TeO2–TaO5/2–ZnO glass system to assess and quantify the relation between Raman gain and optical responses within the glass’ network arrangement. The level of polymerization of the TeO4 chain-like structure in a TeO2 glass system has been identified to be the main parameter for reaching high linear and nonlinear optical constant. We have observed that replacement of TaO5/2 by ZnO strongly modifies the optical properties and primarily, the Raman and hyper-Raman spectra of the glasses. In particular, we clearly demonstrate a linear relationship between Raman gain, linear and second-order optical response of the glass which is directly related to the number density of TeO4 chain-like units. Assuming that only TeO4 chain-like units contribute significantly to the glass’ polarizability, we have found that about 30% of the Te atoms contribute to the hyperpolarizability of the binary system 80TeO2-20ZnO in very good accordance with neutron diffraction results. Voir moins

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 driedoxidant atmosphere (relative humidity <1%) reduces drastically the OH impurities. The effect of reducing the OH content on
the glass properties such as characteristic temperatures, crystallization stability (DT), density, and microhardness… Voir plus

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 driedoxidant atmosphere (relative humidity <1%) reduces drastically the OH impurities. The effect of reducing the OH content on
the glass properties such as characteristic temperatures, crystallization stability (DT), density, and microhardness is investigated. Voir moins

Raman spectra of the tetragonal (D44) structure of paratellurite TeO2 have been revisited avoiding anomalous polarization-selection rules violations previously observed and due to optical activity. We present a complementary hyper-Raman scattering study of paratellurite. Wavenumber and symmetry assignments are given for all expected 21 Raman active optical branches, except one
LO component (out of the eight expected TO–LO pairs) of the polar doublet E modes. Also, the four expected… Voir plus

Raman spectra of the tetragonal (D44) structure of paratellurite TeO2 have been revisited avoiding anomalous polarization-selection rules violations previously observed and due to optical activity. We present a complementary hyper-Raman scattering study of paratellurite. Wavenumber and symmetry assignments are given for all expected 21 Raman active optical branches, except one
LO component (out of the eight expected TO–LO pairs) of the polar doublet E modes. Also, the four expected hyper-Raman active A2 (TO) modes have been observed. Moreover, we have observed a strong Kleinman-disallowed hyper-Rayleigh signal, which is tentatively assigned as a first evidence of hyper-Rayleigh optical activity. Voir moins

Raman gain efficiency and structure of tellurite glasses in the TeO2-TaO5/2-ZnO system have been investigated by Raman and IR spectroscopies. It has been found that replacement of TaO5/2 by ZnO does not significantly modify the respective proportion of TeO4, TeO3 and TeO3+1 entities but induces an important decrease of the TeO4 structural units Raman cross section. Change of the glass structure at the middle range length scale is proposed to be at the origin of the large decrease of the Raman… Voir plus

Raman gain efficiency and structure of tellurite glasses in the TeO2-TaO5/2-ZnO system have been investigated by Raman and IR spectroscopies. It has been found that replacement of TaO5/2 by ZnO does not significantly modify the respective proportion of TeO4, TeO3 and TeO3+1 entities but induces an important decrease of the TeO4 structural units Raman cross section. Change of the glass structure at the middle range length scale is proposed to be at the origin of the large decrease of the Raman cross section of the TeO4 units. Voir moins

In this paper, a detailed study to examine the influence of chalcogen S/Se mole % in the Ge28Sb12S60 −xSex glass system, with x = 0, 15, 30, 45 and 60, is presented that provides insight into the effect of chalcogen content on the glass network and properties. Specifically, we report results of a systematic study to evaluate the relationship between compositional variation, glass properties and dominant bonding configurations. These materials are important to applications in optics… Voir plus

In this paper, a detailed study to examine the influence of chalcogen S/Se mole % in the Ge28Sb12S60 −xSex glass system, with x = 0, 15, 30, 45 and 60, is presented that provides insight into the effect of chalcogen content on the glass network and properties. Specifically, we report results of a systematic study to evaluate the relationship between compositional variation, glass properties and dominant bonding configurations. These materials are important to applications in optics manufacturing where correlation of physical and optical properties is required to predict fabrication behavior and ultimate material performance. It has been found that the dominant bonds in the glass system change upon reaching a specific molar ratio (percentage, %) of chalcogen substitution, between 30 < x < 45 mol%, changing from Ge―Se to Sb―Se bonds as the dominant bond type. This singularity has been observed using micro-Raman spectroscopy and X-ray photoelectron spectroscopy. This effect of the dominant bond configurational change was also shown to impart changes in important physical properties including micro-hardness, thermal properties, and the glass' viscometric behavior. Results indicate that the observed dominant bond change was responsible for a constant value in the evolution of both the micro-hardness and calorimetric glass transition temperature. The viscosity was also affected by the change in dominant bond type, breaking the monotony of the viscosity evolution during the S substitution, due to the total strength of the vitreous system which does not linearly increase. Voir moins

Glass ceramic materials with composition 75TeO2–xBi2O3–(25-x)ZnO (x = 13, 12, 11) possessing transparency in the near- and mid-infrared (MIR) regions were studied in this paper. It was found that as the Bi2O3 content increased in the glass composition, the observed crystallization tendency is enhanced, and high crystal concentrations were obtained for the glasses with high Bi2O3 content while maintaining transparency in the MIR region. Crystal size in the glass ceramic was reduced by adjusting… Voir plus

Glass ceramic materials with composition 75TeO2–xBi2O3–(25-x)ZnO (x = 13, 12, 11) possessing transparency in the near- and mid-infrared (MIR) regions were studied in this paper. It was found that as the Bi2O3 content increased in the glass composition, the observed crystallization tendency is enhanced, and high crystal concentrations were obtained for the glasses with high Bi2O3 content while maintaining transparency in the MIR region. Crystal size in the glass ceramic was reduced by adjusting the heat treatment conditions; the smallest average size obtained in this study is 700 nm. Bi0.864Te0.136O1.568 was identified using X-ray Diffraction (XRD) and found to be the only crystal phase developed in the glass ceramics when the treatment temperature was fixed at 335 °C. The morphology of the crystals was studied using Scanning Electron Microscopy (SEM), and crystals were found to be polyhedral structures with uniform sizes and a narrow size distribution for a fixed heat treatment regime. Infrared absorption spectra of the resulting glass ceramics were studied. The glass ceramic retained transparency in the infrared region when the crystals inside were smaller than 1 μm, with an absorption coefficient less than 0.5/cm in the infrared region from 1.25 to 2.5 μm. The mechanical properties were also improved after crystallization; the Vickers Hardness value of the glass ceramic increased by 10% relative to the base glass. Voir moins

Fabrication of TeO2–Bi2O3–ZnO glass ceramics with high transmittance in the near infrared (NIR) region is reported in the present work. Transparent tetragonal bipyramid crystals, tens of micrometers in size, with a refractive index closely matched to that of the glass matrix were formed using a two-step heat treatment. Nucleation- and growth-like curves for this crystal phase were determined using Differential Scanning Calorimetry (DSC). The crystalline phases present in the glass ceramics were… Voir plus

Fabrication of TeO2–Bi2O3–ZnO glass ceramics with high transmittance in the near infrared (NIR) region is reported in the present work. Transparent tetragonal bipyramid crystals, tens of micrometers in size, with a refractive index closely matched to that of the glass matrix were formed using a two-step heat treatment. Nucleation- and growth-like curves for this crystal phase were determined using Differential Scanning Calorimetry (DSC). The crystalline phases present in the glass ceramics were identified via x-ray diffraction as a function of heat treatment. The lowest absorption coefficient of glass ceramic is approximately 0.5/cm in the near infrared region (1.2 to 2.8 μm). Voir moins