Influence of excitation wavelengths on up-converted luminescence sensing behavior of Er3+ ions in lead-free germanate glass

Temperature-dependent up-conversion luminescence spectra of Er3+ in lead-free germanate glass have been examined under 800 nm and 980 nm diode laser excitation. Green up-conversion luminescence spectra measured in the 500-580 nm ranges correspond to transitions originating from thermally coupled H-2(11/2) and S-4(3/2) levels to I-4(15/2) ground level of Er3+. The relative emission band intensities of H-2(11/2) -> I-4(15/2) and S-4(3/2) -> I-4(15/2) transitions of Er3+ are changed with temperature. The rate of fluorescence intensity ratio varying with temperature was calculated for glass sample excited at 800 nm and 980 nm, respectively. The maximum temperature sensitivity is nearly 20% higher for glass sample pumped at 980 nm than 800 nm.