Spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2-20Al2O3-30CaF2 glass and glass ceramics
Résumé
A spectroscopic investigation of Er3+/Yb3+ co-doped 50SiO2-20Al2O3-30CaF2 glasses and transparent glass ceramics containing CaF2 nanocrystals is presented. The formation of CaF2 nanocrystals in the glass ceramic was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The Judd-Ofelt parameters of the Er3+ ions in the glass and glass ceramic have been calculated; they suggested that Er3+ ions had been incorporated into CaF2 nanocrystals in the glass ceramics. The upconversion luminescence intensity of the Er3+/Yb3+ co-doped glass ceramic was much stronger than that of the Er3+/Yb3+ co-doped glass. The upconversion luminescence mechanism has been ascribed to a two-photon absorption process for the green and red luminescence and a three-photon absorption process for the blue luminescence.