Infrared to Visible Up-Conversion Emission in Er~(3+)/Yb~(3+) CoDoped Fluoro-Phosphate Glass-Ceramics

摘要

Erbium Er~(3+) and ytterbium Yb~(3+) codoped fluoro-phosphate glasses belonging to the system NaPO_3-YF_3-BaF_2-CaF_2 have been prepared by the classical melt-quenching technique. Glasses containing up to 10 wt.% of erbium and ytterbium fluorides have been obtained and characterized using differential scanning calorimetry (DSC) and UV-visible and near-infrared spectroscopy. Transparent and homogeneous glass-ceramics have been then reproducibly synthetized by appropriate heat treatment above glass transition temperature of a selected parent glass. Structural investigations of the crystallization performed through X-ray diffractometry (XRD) and scanning electron microscopy (SEM) have evidenced the formation of fluorite-type cubic crystals based during the devitrification process. Finally, infrared to visible up-conversion emission upon excitation at 975 nm has been studied on the Er~(3+) and Yb~(3+) codoped glass-ceramics as a function of thermal treatment time. A large enhancement of intensity of the up-conversion emissions - about 150 times- has been observed in the glass-ceramics if compared to the parent glass one, suggesting an incorporation of the rare-earth ions (REI) into the crystalline phase.