Influence of temperature on upconversion luminescence in tellurite glass co-doped with Yb3+/Er3+ and Yb3+/Tm3+

The fluorescence intensity ratio (FIR) of the green upconversion in Yb3+/Er3+ and blue upconversion in the Yb3+/Tm3+ co-doped tellurite glass as a function of temperature in the range of 20–220 °C was investigated. The influence of temperature on FIR upconversion emission spectra of the thermally coupled Er3+: 2H11/2 and 4S3/2 levels enabled to achieve maximum sensitivity of 0.0036 °C−1 at 225 °C. Despite the lack of thermally coupled levels Yb3+/Tm3+ co-doped tellurite glass is proposed for construction of a temperature sensor. The maximum sensitivity of 0.0044 °C−1 at 240 °C was obtained using the FIR technique of the upconversion emission at 651 nm (Tm3+: 1G4→3F4) and 698 nm (Tm3+: 3F3→3H6).