Green and red up-conversion emissions and thermometric application of Er³⁺-doped silicate glass

The green and red up-conversion emissions centred at about 534, 549 and 663\,nm of wavelength, corresponding respectively to the ^2H_11 / 2 \to ^4I_15 / 2, ^4S_3 / 2 \to ^4I_15 / 2 and ^4F_9 / 2 \to ^4I_15 / 2 transitions of Er^3 + ions, have been observed for the Er^3 + -doped silicate glass excited by a 978\,nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296--673\,K, which shows that Er^3 + -doped silicate glass can be used as a sensor in high-temperature measurement.