Abstract:In this work we present, for the first time to our knowledge, laser emission under wavelength selective laser-pulsed pumping in Nd 3+ -doped TeO 2 -ZnO-ZnF 2 bulk glass for two different Nd 3+ concentrations. The fluorescence properties of Nd 3+ ions in this matrix which include, JuddOfelt calculation, stimulated emission cross-section of the laser transition and lifetimes are also presented. The site-selective emission and excitation spectra along the 4 I 9/2 → 4 F 3/2 absorption band show the inhomogeneous behaviour of the crystal field felt by Nd 3+ ions in this fluorotellurite glass which allows for spectral tuning of the laser output pulse as a function of the pumping wavelength. The emission cross-section obtained from the Judd-Ofelt analysis and spectral data (4.9x10 −20 cm 2 ) is in fairly good agreement with the value obtained from the analysis of the laser threshold data (4x10 −20 cm 2 ).

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Transparent glass-ceramics containing Er 3+ -doped sodium lutetium fluoride nanocrystals for photonic applications have been synthesized. Glass transition temperature, softening temperature, and crystallization temperature were estimated by dilatometry and differential thermal analysis. Proper heat treatments were selected to crystallize lutetium fluoride nanocrystals. X-ray diffraction analysis was carried out to identify the crystalline phase and the crystal size. HRTEM indicates that the base glass is phase separated in droplets enriched in Lu, Na, F, and also Er ions. The thermal treatment induces the crystallization *mpascual@icv.csic.es inside the droplets. The optical characterization, which includes absorption and steady-state and time-resolved emission spectroscopy under one-and two-photon excitation, shows the differences between the phase-separated base glass and its corresponding glass-ceramic. The reduction of the Judd-Ofelt parameter Ω 2 together with the increase of the fluorescence lifetimes as compared to the glass sample confirms the presence of Er 3+ ions in a crystalline environment in the glass-ceramic samples. Moreover, an enhancement of the green and red up-converted emissions (as well as the weak blue emission) is observed in the glass-ceramic, indicating the Er 3+ incorporation into the nanocrystals. The possible excitation mechanisms responsible for this up-conversion luminescence are discussed on the basis of lifetime measurement results.

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