Influence of 980 nm pump power on optical thermometry based on NaYF4:Yb3+/Er3+ nanoparticles

For optical thermometry, the pump light source has an important influence on the temperature measurement performance. In this study, we investigated the influence of 980 nm pump power on fluorescence intensity ratio (FIR) thermometry based on NaYF4 :5% Yb3+/2% Er3+ nanoparticles. The thermally coupled level (TCL) of H-2(11/2) and S-4(3/2) of Er3+ was selected to evaluate the temperature. The correspondence between the FIR and temperature of this sample near room temperature was observed. In addition, the relationship between the FIR and pump power was analysed. The temperature increment induced by the laser thermal effect and the uncertainty of the FIR of the sample were studied with an increasing power density. The results indicate that the uncertainty ratio of the FIR (AFIR/FIR) decreases rapidly with the pump power density, which implies that the precision of the temperature measurement is improved. While the temperature increment induced by the pump power increases linearly with a slope of 6 K/(W/cm(2)), this will reduce the temperature sensing accuracy. Clearly, this contradiction in utilizing a 980 nm pump power should be balanced in practical applications of optical thermometry.