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 H-2(11/2),S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) 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 H-2(11/2) > I-4(15/2) and S-4(3/2) > I-4(15/2) 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 x 10(-4)K(-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. (C) 2017 Elsevier B.V. All rights reserved.