Fluorescence characteristics of $Tm3+$ in different local environments

Fluorescence from ions in both the crystal and glass phases was investigated by selective excitation of $Tm3+$ doped transparent oxyfluoride glass ceramics containing $LaF3$ nanocrystals. The spectroscopic properties of ions in different local environments were studied. It was found that the glass phase favored blue up-conversion of $Tm3+$ when a pulsed red light was applied. The most efficient up-conversion was obtained when the excited state absorption was resonant with the excitation.