Optical transition and upconversion luminescence in Er 3+ doped and Er 3+–Yb 3+ co-doped fluorophosphate glasses

Abstract

Fluorophosphates glasses YF 3–BaF 2–Ba(PO 3) 2 doped with Er 3+ and Er 3+–Yb 3+ were prepared and the structures of the samples were briefly investigated. The experimental intensity parameters were calculated according to the Judd–Ofelt theory, from which the radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of Er 3+ were obtained. Bright green and red upconversion emissions was observed in Er 3+–Yb 3+ co-doped samples excited by 980 nm laser diode, and two-photons absorption processes were determined for the emissions by examining the dependence of the emission intensity on the excitation power. The concentration effects on the intensity and decay time of the upconversion emission revealed that growing Er 3+ concentration declined the probability of sequential energy transfer from Yb 3+ to Er 3+, and thus increasing the intensity ratio of the red emission to the green ones. The temperature effects on the intensity ratios of different emission bands showed that the maximum transducer sensitivity based on the fluorescence intensity ratio (FIR) was calculated to be 0.0015/°C at 6 °C.