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Properties of the glasses are experimentally investigated when Ga is gradually substituted by Ge in Ga 8 Sb 32 S 60 chalcogenide glass. The glass structure is also studied to elucidate the variations of the properties. While the substitution of Ga by Ge does not remarkably change the glass transition temperature T g , the thermal stability against crystallization becomes optimum when half of the Ga atoms are replaced by Ge atoms. The short-wavelength absorption edge λ S (or optical bandgap E g ) exhibits a remarkable decrease when a small amount of Ge is added, however, its value does not change significantly with further Ga substitution. As Ga is gradually replaced by Ge, the long-wavelength cut-off edge λ L , the density ρ , the linear refractive index n , and the third-order nonlinear refractive index n 2 decrease. It is shown that the property variations of the glasses could be explained by the evolution of the glass structure. [ABSTRACT FROM AUTHOR]

The composition dependence of density ( d ), refractive index ( n ) and optical bandgap ( E g ) of Ge-As-S chalcogenide glasses is investigated. It is shown that d correlates linearly with sulfur content but relatively poorly with the mean coordination number (MCN). It is also shown that n does not correlate directly with d , and instead a semi-empirical relation based on the molar refractivity ( R ) of Ge, As and S is derived, permitting to predict n from d with < 1% error. A convenient method based on diffuse reflectance is proposed to measure E g of Ge-As-S glasses with good accuracy. It is shown that the value of E g is dominated by the S content. These findings make it convenient to tailor the physical and optical properties of glasses in Ge-As-S system. [ABSTRACT FROM AUTHOR]

Abstract: Mapping of refractive index patterns with sub-wavelength resolution is achieved using Near-field Scanning Optical Microscopy (NSOM) in reflection mode. Imaging of index pattern is performed on surface gratings photo-imprinted in As2S3 films. The NSOM is adapted with a near infrared laser which wavelength (785nm) is chosen to be within the transparency window of the glass film therefore allowing consistent measure of reflected light. Quantitative measurements of photo-induced index changes can then be obtained from knowledge of the initial film index. Images of gratings with a period of 0.5micron are easily collected therefore demonstrating sub-wavelength spatial resolution. The technique permits to concurrently obtain a topographic image and index image of the gratings thereby permitting to quantify the extent of photodarkening and photoexpansion simultaneously. It is shown that relief gratings tend to vanish in films aged in air for several months however the index gratings remain. [Copyright &y& Elsevier]

Gradient refractive index materials (GRINs) are rapidly evolving in optical achromats and compact imaging systems. And GRINs with multi-band imaging mean higher integration for advanced optical imaging systems. In this paper, GRINs covering mid-wave infrared (MWIR) and long-wave infrared (LWIR) were prepared by thermal diffusion method based on Ge 20 Se 80-x Te x glasses. Similar glass transition temperatures (ΔT g = 1 °C) and coefficients of thermal expansion (ΔCTE = 5.47 ppm/K) permit efficient bonding and diffusion processes between the glasses. The GRINs were visualized by infrared imagers, and the axial diffusion results were accurately characterized by Raman spectroscopy and energy dispersive spectrometer (EDS). The refractive index difference (Δn) of the GRINs reaches 0.23 and the diffusion depth reaches 3.53 mm. Diffusion coefficients and activation energy were calculated and discussed. Dispersion property is initially evaluated by Abbe number and partial dispersion. [ABSTRACT FROM AUTHOR]

In this work, a new chalcohalide glass system, Ga 2 S 3 Sb 2 S 3 CsCl (GSSC), is reported. The glass-forming ability and the physical properties are investigated; and the potential applications of these glasses are evaluated. The glass forming ability can be remarkably improved when CsCl is added into Ga 2 S 3 Sb 2 S 3 glasses, and the compositions with more than 30% CsCl possess quite good thermal stability against crystallization. The studied GSSC glasses have transition temperatures of 217–250 °C, densities of 3.42–3.97 g/cm 3 , micro-hardness of 1.12–1.88 GPa, a transparent window of ∼0.56–13.4 μm, linear refractive indices of 1.99–2.58 @ 10 μm, nonlinear refractive indices of 1.1–11.9 × 10 −14 cm 2 /W @ 1030 nm, and zero group-velocity-dispersion wavelengths of 3.37–5.15 μm. The wide transparent window and the superior optical nonlinear property make these glasses good optical materials for infrared imaging and nonlinear photonics. [ABSTRACT FROM AUTHOR]

The refractive indices ( n ) and thermo-optic coefficients ( ζ ) of Ge 14 As x Se 86 − x and Ge x As 12 Se 88 − x glasses are measured in the 2–12 μm mid-infrared range. The composition dependences of the two parameters are investigated and strategies for tailoring them are proposed. The density ( d ) shows a maximum at the stoichiometric composition when Ge content is fixed; while it exhibits a minimum at the mean coordination number (< r >) of 2.67 when As concentration is fixed. The volume thermal expansion coefficient ( β ) broadly decreases with increasing < r >. Two semi-empirical relations are used to predict n and ζ from the glass composition. The n of a Ge-As-Se glass could be predicted with an error of < 1% from the d of the glass and the molar refractivity ( R i ) of the constituent elements. The estimated values of R i for Ge, As and Se between 2 and 12 μm range from 10.12–10.52, 11.71–11.91, and 11.17–11.25 cm 3 /mol, respectively. The ζ of a Ge-As-Se glass could be forecasted with an error of < 6 ppm/K from the β of the glass and the thermal coefficients of the molar refractivity ( φ i ) of the constituent elements. The estimated values of φ i for Ge, As and Se between 2 and 12 μm range from 26.2–26.7, 54.9–55.7 and 85.4–86.8 ppm/K, respectively. [ABSTRACT FROM AUTHOR]

A Co2+:ZnS-doped chalcogenide glass with broadband mid-infrared emission was prepared by using a hot uniaxial pressing process. The refractive index difference (Δn) between matrix glass (As 2 S 5) and crystal (Co2+:ZnS) was controlled to be 0.0042 in the emission spectral range of Co2+ to minimize the scattering effect. An ultrabroadband mid-infrared emission of 2–4 μm was observed at room temperature in the samples after excitation by using a commercially available laser diode of 1550 nm. The significant changes in the lifetime and fluorescence intensity of Co2+:ZnS-doped chalcogenide glass were measured in the temperature range of 90–290 K. A resolution of approximately 0.18 K was observed when used as a temperature detector. Furthermore, a gas-sensing device was built by using the strong and broad emissions of the sample, and the detection sensitivity of butane reached 56 ppm. These results show that this glass-ceramics can be used as optical sensing of gas and temperature. [ABSTRACT FROM AUTHOR]

In this study, AlON powders with different AlN contents were synthesized by the carbothermal reduction nitridation method and used to prepare transparent AlON ceramics. Lattice parameters of AlON powders were calculated from XRD patterns to evaluate the effects on microstructure. The influences of the AlN content on the properties of the resulting AlON ceramics was investigated in aspect of density, mechanical properties and optical properties. With an increase in the AlN content, the density of the AlON ceramics increased, the grain size decreased, and the hardness and fracture toughness increased. Transparent AlON ceramics were obtained at the AlN content of 21.6–29.7 mol%. The refractive index of the AlON ceramics increased from 1.688 to 1.702 at 4000 nm with an increase of AlN content. The correlation between the composition and properties of the AlON ceramics obtained in this study will provide both theoretical and experimental reference for industrial AlON ceramic manufacturing. [ABSTRACT FROM AUTHOR]