Modeling And Experimental Determination Of Physical Properties Of Ge x -Ga y -Se 1-x-y Chalcogenide Glasses I: Structure And Mechanical Properties

A series of ten GexGaySe1-x-y glasses within the topological constraint regime of = 2.3 to 2.8 were processed for physical property testing to compare measured to calculated property values enabling further understanding of structure-related mechanical property evolution. Average bond energies were calculated for each glass to elucidate structure and property relationships. Raman analysis was performed to correlate the topological constraint theory to experimentally determined structural units. Young\u27s modulus and Vickers hardness, respectively, were shown to increase with increasing coordination number from 14.42 GPa and 911 MPa at = 2.4 to 29.44 GPa and 2295 MPa at = 2.8. Poisson\u27s ratio decreased linearly with increasing coordination number from 0.2996 at = 2.4 for Ge0.15Ga0.05Se0.85 to 0.2477 at = 2.8 for Ge0.25Ga0.15Se0.60 . These properties indicate a strong dependence on the topological network of the glass, in which continued crosslinking and interconnectivity lead to a direct increase or decrease of the respective mechanical property. It was found that theoretical values were in good agreement with measured experiment values, elucidating the impact of the energy required to propagate a crack tip or alter bond lengths and atom positions

Modeling And Experimental Determination Of Physical Properties Of Ge x Ga y Se 1-x-y Chalcogenide Glasses II: Optical And Thermal Properties

This study systematically analyzed the correlation between topological structure and chemical ordering on the optical and thermal properties of synthesized material in the glass forming region of the GexGaySe1-x-y ternary. A series of ten compositions from 5 to 30 mol% Ge and 5 to 15 mol% Ga were examined within the ternary, showing broadband infrared properties with transmission from 1 to 25 μm. Topological constraint theory applied to compositions examined exhibited sharp inflection at the average coordination number of = 2.67 defined as the chemical threshold where the glass network consists of tetrahedral Ge(Ga)Se2 units. These observations indicate that thermal and optical properties in these chalcogenide glasses are highly sensitive to the chemical ratio of homopolar versus heteropolar bonds, Ge to Ga ratio, as well as the dimensionality of the topological structure. Glass transition and crystallization temperature values compare well with previous literature on similar Ge–X–Se systems. This is a comprehensive study that systematically examined thermal conductivity, heat capacity, absorption coefficient, and refractive index within the GexGaySe1-x-y system, correlating these properties with structural network calculations. The presented methodology and findings will enable the compositional design of materials for infrared systems using GexGaySe1-x-y glasses with broadband transmission

Two Photon Absorption in Chromophore Doped Solid Matrices

Over the past decades organic materials have shown an important potential for applications in the field of nonlinear optics. Two-photon absorbing materials can be optically addressed in three dimensions of space, which make them unique for many new applications, including 3D displays, optical memories, bio-sensors, etc. Fluorescent organic chromophores can be synthesized with structures especially optimized for this nonlinear optical property. Yet, for some applications, they have to be incorporated in solid state matrices. We especially investigate hybrid organic/inorganic doped matrices synthesized by solgel process. However , the linear transmission for such molecules is often significantly less than unity. Two-photon absorption (TPA) offers the advantage of very high transmission at low incident intensity, while being sensitive to high intensity laser pulses. Our aim is to record a 3D layered pattern of optical memory inside the sample by the use of the picosecond pulsed ND3+:YAG laser at 532nm, or 1064nm

Elaboration and Optimization of Tellurite-based Materials for Raman Gain Application

L expansion de nouvelles technologies et la demande incessante d une transmission d informations plus rapide font que les systèmes de télécommunications nécessitent plus de débit sur de plus longues distances. L amplification optique et notamment l amplification optique par effet Raman représente une intéressante possibilité à repousser les limites de distance et de debit.Les verres à base d oxyde de tellure sont des matériaux prometteurs pour les applications d amplification optique par effet Raman; en particulier grâce à leurs fortes propriétés optiques linéaires et non linéaires, leurs fenêtres de transparence allant dans le proche et milieu infra-rouge du spectre de transmission. De plus, leurs propriétés thermiques et en particulier leurs faibles temperatures de transition vitreuse permettent une facilité de fibrage. L estimation de l intensité du gain Raman et sa zone spectrale mise en jeu sont généralement approchées à partir du spectre de diffusion Raman spontanée du matériaux. La compréhension des relations existantes entre la structure vitreuse, la réponse vibrationnelle et les propriétés d optique non linéaire, représente un point clé au développement et à l optimisation des verres de tellure pour l amplification Raman. Cette dissertation apporte une réponse détaillée à la question fondamentale de l étude doctorale: Quel est l impact de la structure vitreuse sur les propriétés d amplification Raman dans les verres d oxyde de tellure?Tellurite-based oxide glasses have been investigated as promising materials for Raman gain applications, due to their good linear and nonlinear optical properties and their wide transparency windows in the near- and midwave infrared spectral region. Furthermore, their interesting thermal properties, i.e. low glass transition temperature and ability to be drawn into optical fibers, make tellurite-based glasses excellent candidates for optical fiber amplifiers. The estimation of the strength and spectral distribution of Raman gain in materials is commonly approximated from the spontaneous Raman scattering cross-section measurement. For development of tellurite-based glasses as Raman amplifiers, understanding the relationship between glass structure, vibrational response, and nonlinear optical properties (NLO) represents a key point. This dissertation provides an answer to the fundamental question of the PhD study: What is the impact of the glass structure on Raman gain properties of tellurite glasses?BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Physical and optical properties of sol-gel nano-silver doped silica film on glass substrate as a function of heat-treatment temperature

Nano-silver doped silica films were deposited on glass slides using a sol-gel process and heat-treated at different temperatures. The films were characterized by ultraviolet-visible spectroscopy, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy for their optical, chemical, and structural properties. The absorption peak of silver colloids (wavelength from 400 to 460 nm) was present and a blueshift and intensity reduction of the absorption peak was observed during heat-treatment. Particle size reduction and surface morphology changes in the films were observed by AFM as a function of varying heat treatment temperatures. Silver nanoparticles were formed through spontaneous reduction of silver ions. The oxidation of silver occurs during heat-treatment, causing a reduction of absorption intensity. An interdiffusion between the Ag in the film and Na in the substrate glass was observed by XPS and RBS. Sodium in the coating likely increased the stability of silver oxide at high temperature treated samples

X-ray photoelectron spectroscopic investigation of surface chemistry of ternary As-S-Se chalcogenide glasses

Chalcogenide glasses belong to an important class of materials, due to their good infrared transmission, and low-phonon energy as compared to other oxide glasses. Structural and chemical variations imposed by glass processing conditions, e.g., film deposition, can lead to changes in the linear and nonlinear optical properties. X-ray photoelectron spectroscopy (XPS) has been employed to study As-S-Se glasses of differing chemical compositions, in the film and the bulk form, to understand any variations in chemical bond configuration and their electronic structure. The molecular environments of As and Se for As-S-Se samples with varying S/Se ratio (fixed As content) and As content (fixed S/Se ratio) are studied by monitoring the XPS chemical shifts. The surface chemistry of the bulk and thin-film chalcogenide glasses are also compared to determine the effect of glass processing conditions for better chalcogenides for potential waveguide applications

A randomized trial comparing structured and lifestyle goals in an internet-mediated walking program for people with type 2 diabetes

Abstract Background The majority of individuals with type 2 diabetes do not exercise regularly. Pedometer-based walking interventions can help; however, pedometer-based interventions targeting only total daily accumulated steps might not yield the same health benefits as physical activity programs specifying a minimum duration and intensity of physical activity bouts. Methods This pilot randomized trial compared two goal-setting strategies: 1) lifestyle goals targeting total daily accumulated step counts and 2) structured goals targeting bout steps defined as walking that lasts for 10 minutes or longer at a pace of at least 60 steps per minute. We sought to determine which goal-setting strategy was more effective at increasing bout steps. Participants were sedentary adults with type 2 diabetes. All participants: wore enhanced pedometers with embedded USB ports; uploaded detailed, time-stamped step-count data to a website called Stepping Up to Health; and received automated step-count feedback, automatically calculated goals, and tailored motivational messages throughout the six-week intervention. Only the automated goal calculations and step-count feedback differed between the two groups. The primary outcome of interest was increase in steps taken during the previously defined bouts of walking (lasting at least 10 minutes or longer at a pace of at least 60 steps per minute) between baseline and end of the intervention. Results Thirty-five participants were randomized and 30 (86%) completed the pilot study. Both groups significantly increased bout steps, but there was no statistically significant difference between groups. Among study completers, bout steps increased by 1921 ± 2729 steps a day. Those who received lifestyle goals were more satisfied with the intervention (p = 0.006) and wore the pedometer more often (p < 0.001) than those who received structured goals. Conclusion In this six-week intervention, Lifestyle Goals group participants achieved increases in bout steps comparable to the increases seen in the Structured Goals group, representing almost a mile a day of additional moderate intensity bout activity. Pedometer-based walking programs that emphasize total accumulated step counts are more acceptable to participants and are as effective at increasing moderate intensity bouts of physical activity as programs that use structured goals. Trial registration NCT00151021http://deepblue.lib.umich.edu/bitstream/2027.42/112366/1/12966_2007_Article_136.pd

A randomized trial comparing structured and lifestyle goals in an internet-mediated walking program for people with type 2 diabetes

BACKGROUND: The majority of individuals with type 2 diabetes do not exercise regularly. Pedometer-based walking interventions can help; however, pedometer-based interventions targeting only total daily accumulated steps might not yield the same health benefits as physical activity programs specifying a minimum duration and intensity of physical activity bouts. METHODS: This pilot randomized trial compared two goal-setting strategies: 1) lifestyle goals targeting total daily accumulated step counts and 2) structured goals targeting bout steps defined as walking that lasts for 10 minutes or longer at a pace of at least 60 steps per minute. We sought to determine which goal-setting strategy was more effective at increasing bout steps. Participants were sedentary adults with type 2 diabetes. All participants: wore enhanced pedometers with embedded USB ports; uploaded detailed, time-stamped step-count data to a website called Stepping Up to Health; and received automated step-count feedback, automatically calculated goals, and tailored motivational messages throughout the six-week intervention. Only the automated goal calculations and step-count feedback differed between the two groups. The primary outcome of interest was increase in steps taken during the previously defined bouts of walking (lasting at least 10 minutes or longer at a pace of at least 60 steps per minute) between baseline and end of the intervention. RESULTS: Thirty-five participants were randomized and 30 (86%) completed the pilot study. Both groups significantly increased bout steps, but there was no statistically significant difference between groups. Among study completers, bout steps increased by 1921 ± 2729 steps a day. Those who received lifestyle goals were more satisfied with the intervention (p = 0.006) and wore the pedometer more often (p < 0.001) than those who received structured goals. CONCLUSION: In this six-week intervention, Lifestyle Goals group participants achieved increases in bout steps comparable to the increases seen in the Structured Goals group, representing almost a mile a day of additional moderate intensity bout activity. Pedometer-based walking programs that emphasize total accumulated step counts are more acceptable to participants and are as effective at increasing moderate intensity bouts of physical activity as programs that use structured goals. TRIAL REGISTRATION: NCT0015102

Celebrating Optical Glass - the International Year of Glass (2022) : feature issue introduction

We introduce the Optical Materials Express feature issue that celebrates historic and recent advances in optical glass. In honor of the United Nations declaring 2022 to be the International Year of Glass (IYOG), this issue comprises a collection of twenty-seven manuscripts that highlight processing, characterization/metrology and applications where glass has changed our world.publishedVersionNon peer reviewe

Nonlinear characterization of GeSbS chalcogenide glass waveguides

GeSbS ridge waveguides have recently been demonstrated as a promising mid – infrared platform for integrated waveguide – based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.55 μm. Using self – phase modulation experiments, we characterize a waveguide nonlinear parameter of 7 W[subscript −1]/m and nonlinear refractive index of 3.71 × 10[superscript −18] m[superscript 2]/W. GeSbS waveguides are used to generate supercontinuum from 1280 nm to 2120 nm at the −30 dB level. The spectrum expands along the red shifted side of the spectrum faster than on the blue shifted side, facilitated by cascaded stimulated Raman scattering arising from the large Raman gain of chalcogenides. Fourier transform infrared spectroscopic measurements show that these glasses are optically transparent up to 25 μm, making them useful for short – wave to long – wave infrared applications in both linear and nonlinear optics.SUTD-MIT International Design Centre (IDC