An abnormal fluorescence intensity ratio between two green emissions of Er3+ caused by heating effect of 980 nm excitation

An abnormal fluorescence intensity ratio (FIR) between two green emissions of Er3+ at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has seldom been done to clarify this abnormal phenomenon. In this paper, green upconversion luminescence of the beta-NaLuF4:20% Yb3+, 2%Er3+ powder sample was investigated under 980 nm excitation at different circumstances, different pump power densities and different temperatures as well as different air pressures. The corresponding local temperature calculated using FIR technique increased gradually with the enhancement of the pump power density. It was demonstrated that high pump power density of 980 nm laser led to the increase of local temperature of the luminescent material, which further gave the abnormal FIR.