Optical temperature sensing in Er3+-Yb3+ codoped CaWO4 and the laser induced heating effect on the luminescence intensity saturation

CaWO4 phosphors doping with different Er3+ and Yb3+ ion concentrations were synthetized through high temperature solid-state reaction technique. Excited by 980 nm laser, the influence of rare earth dopant concentration on the thermometry behavior of Er3+ green upconversion emissions was discussed via the fluorescence intensity ratio method. Superior temperature sensing ability could be achieved in CaWO4: 0.1 mol% Er3+-3 mol% Yb3+, the maximum sensitivity of which is about 1.05 × 10−2 K−1 at 439 K. Meanwhile, the pumping laser induced thermal effect on the saturation of upconversion emission intensity has been preliminarily studied. The temperature of the irradiation spot on sample caused by the exposure of excitation laser is observed to be greatly enhanced as the pumping power increased. Based on the steady-state rate equations and the temperature dependence of luminescence decay curves, theoretical calculations have been performed. The results confirm that the laser induced heating effect plays an important role in the luminescence intensity saturation phenomenon.