Study on optical properties and upconversion luminescence of Er 3+ /Yb 3+ co-doped tellurite glass for highly sensitive temperature measuring

Er3+/Yb3+ co-doped tellurite glass is prepared by conventional melt-quenching method. The thermal and optical properties of the glass are investigated for temperature sensing. The Judd-Ofelt theory is applied for spectral analysis and the obtained intensity parameters (Ω2 = 6.48 × 10−20 cm2, Ω4 = 1.82 × 10−20 cm2, Ω6 = 1.27 × 10−20 cm2) are used to estimate the spectroscopic parameters of Er3+ ions in the glass. The upconversion (UC) luminescence of the glass is investigated under the laser diode (LD) excitation at 976 nm. The absolute quantum yield for UC luminescence is determined to be 0.0049% when the pump power density is 10 W/cm2. The dependences of green and red UC emission intensities on pump power indicate that both of the red and green UC emissions of Er3+ ions are mostly contributed by the co-existing two and three-photon involved energy transfer processes between the Yb3+ and Er3+ ions. Furthermore, the temperature-dependent green UC emissions of the glass are studied and the results show that the glass is an excellent candidate for construction of temperature sensors based on the self-referenced fluorescence intensity ratio (FIR) technique.