Influence of temperature on up-conversion luminescence in Er3+/Yb3+ doubly doped lead-free fluorogermanate glasses for optical sensing

Green and red up-conversion luminescence spectra corresponding to 2H11/2,4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions in Er3+/Yb3+ co-doped lead-free fluorogermanate glasses have been examined as a function of Yb3+ concentration and temperature. The green-to-red luminescence intensity ratio diminishes with increasing Yb3+ concentration. The luminescence intensity ratio for bands related to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ was determined and temperature sensitivity parameters were calculated. The maximal temperature sensitivities for Er3+/Yb3+ co-doped glass samples increase with increasing Yb3+ concentration and the highest value of 42.5 × 10−4K−1 at room temperature was obtained for 0.5Er-3Yb system. Based on gathered data it was concluded that Er3+/Yb3+ co-doped lead-free fluorogermanate glasses are promising for optical temperature sensing.