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Abstract Absorption and emission spectroscopy of Tm3+ dopants in ultratransparent oxyfluoride glass ceramics indicates that most of the active dopants have been incorporated into the nanocrystals. The size of the nanocrystals has been estimated based on experimental studies of polarized and depolarized low-frequency Raman scattering of the Tm3+-doped glass ceramics in the range 0.5–100 cm−1. Symmetric and quadrupolar acoustic vibrations have been observed and are ascribed to the respective modes of the nanoparticles, which are argued to be β-PbF2 nanocrystals. The size distribution of the nanoparticles has been deduced from the shape of the acoustic bands. The Raman data show that the mean size of the PbF2 nanocrystals increases and that the width of the size distribution decreases with the time and temperature of the heat treatment. [ABSTRACT FROM AUTHOR]

Abstract Ultratransparent glass ceramics activated with thulium and erbium ions were fabricated. The precursor oxyfluoride glass was 32SiO2 · 9AlO1.5 · 31.5CdF2 · 18.5PbF2 · 5.5ZnF2 · 3.5ReO1.5 with Re = Tm or Er. Upon heat treatment, Er3+ and Tm3+ nucleate the growth of nanocrystalline β-PbF2, which acts as a host for rare-earth ions. The spectroscopic properties of the thulium and erbium ions, studied via UV-VIS-NIR absorption and luminescence spectroscopy, show that most of the active ions are embedded in the crystalline phase. From the absorption measurement, we extracted the cross sections of Tm3+ ions embedded in the crystalline and glassy phases. The comparison between the experimental lifetimes before and after thermal treatment gave as a result that the ceramming process increases the quantum efficiency of the Tm3+ electronic transitions. In the case of Er3+-activated glass ceramics, the 4I13/2 ⇄ 4I15/2 telecom transition broadens and flattens. [ABSTRACT FROM AUTHOR]

Abstract Two Er3+/Yb3+ monolithic silica-alumina xerogels doped with different Yb3+ concentrations were prepared by sol–gel route. The samples were thermally treated in air at 950°C for 120 h, and Raman and UV-visible-NIR spectroscopy were used to monitor the degree of densification of the glasses and the residual OH [ABSTRACT FROM AUTHOR]