International audienceAn innovative glass/glass ceramic based on the GeSe2-Ga2Se3-CsCl system is reported. This material is the first reported glass/glass ceramic transparent from the visible to the far-IR, has improved mechanical properties over selenide glasses, and is compatible with high-precision molding, making it suitable for applications in thermal imaging

Transparent glass ceramics have been prepared in the Ga(2)S(3)-GeS(2)-CsCl pseudoternary system using appropriate heat treatment time and temperature. In situ X-ray diffraction at the heat treatment temperature and (133)Cs and (71)Ga solid-state nuclear magnetic resonance have been performed in function of annealing time to understand the crystallization process. Both techniques have evidenced the nucleating agent role played by gallium with the formation of Ga(2)S(3) nanocrystals. On the other hand, cesium is incorporated very much later into the crystallites during the ceramization. Moreover, the addition of CsCl, which is readily integrated into the glassy network, permits us to shift the optical band gap toward shorter wavelength. Thus, new glass ceramics transmitting in the whole visible range up to 11.5 mum have been successfully synthesized from the (Ga(2)S(3))(35)-(GeS(2))(25)-CsCl(40) base glass composition.

Sub-band-gap irradiation of a series of bulk Ge-As-Se glass samples with a tunable laser source shows that photostructural processes in chalcogenide glasses are strongly dependent on the covalent network connectivity. The photoexcitation process is affected by the bond density as well as the network rigidity. Photostructural changes such as photodarkening and photoexpansion decrease and tend to vanish in overcoordinated glass in accordance with the rigidity percolation threshold. Also, the intensity required to achieve photofluidity is linearly dependent on the bond density. These results provide quantitative support for a description of photofluidity as a summative bond breaking process.

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Microstructured optical fibers (MOFs) are traditionally prepared using the stack and draw technique. In order to avoid the interfaces problems observed in chalcogenide glasses, we have developed a new casting method to prepare the chalcogenide preform. This method allows to reach optical losses around 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various As(38)Se(62) chalcogenide microstructured fibers have been prepared in order to combine large non linear index of these glasses with the mode control offered by MOF structures. Small core fibers have been drawn to enhance the non linearities. In one of these, three Stokes order have been generated by Raman scattering in a suspended core MOF pumped at 1995 nm.

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International audienceIn this paper, the mechanical and thermo-mechanical properties of glasses and glass-ceramics belonging to the Ge-Ga-Se system are studied. Pure glasses slightly transparent in the visible range up to 16 μm have been synthesized. Glass-ceramics were made using an appropriate heat-treatment time and temperature from the 80GeSe2-20Ga2Se3 base glass in order to improve the mechanical properties. The optical and mechanical properties of glasses and glass-ceramics such as hardness and toughness were investigated. X-ray diffraction (XRD) versus temperature experiments were performed to understand the crystallization evolution as a function of heat-treatment time. GeGa4Se8 and GeSe2 crystalline phases have been determined with XRD. As a result, glass-ceramics with 40% density of crystals present a very low thermal expansion coefficient (11.8 × 10−6± 0.5 K−1) and an excellent infrared transmission in the 3-5 and 8-13 μm regions

International audienceGlass-ceramics were fabricated from the 80GeS2⋅20Ga2S3 chalcogenide glass using an appropriate heat-treatment at a fairly low temperature (T g+30°C) for different durations. Compared with the base glass, they present much-improved thermal shock resistance and fracture toughness, and meanwhile remain an excellent mid-IR transmission in 2-10-μm spectral region. XRD results indicate that the enhanced mechanical properties are mainly due to the appearance of Ga2S3 crystals, and only a very small amount of GeS2 was precipitated on the surface. Bulk and powder samples heat-treated at 458°C for different durations were used to study the evolution of the two crystallization peaks using DSC measurement. It is found that the precipitation of Ga2S3 phase is responsible for the exotherm of first crystallization peak and that of GeS2 phase for the second one. The crystallization mechanism was also examined using the nonisothermal method, and the considerably low activation energy (E c) and high crystallization rate constant (K) for the first crystallization peak illustrate a much easier precipitation of Ga2S3 phase than that of GeS2 phase, which is in good accordance with the ceramization process