Quantification of upconversion photon and thermosensitive feedback in Er³⁺/Yb³⁺ doped fluorotellurite glasses

Multi-photon-excited green and red upconversion (UC) emissions have been quantified and adaptive temperature sensing performance has been investigated in Er³⁺/Yb³⁺ doped fluorotellurite (BZLFT) glasses under the excitation of 978 nm laser. The net emission photon numbers of ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transition emissions are identified to be 83.2 × 10¹², 753.2 × 10¹² and 136.8 × 10¹²cps in 0.4 wt% Er₂O₃-0.4 wt% Yb₂O₃ co-doping case under the excitation power density of 7.82 W/mm². The quantum yields (QYs) and luminous fluxes for visible UC emissions of Er³⁺ are identified as a positive dependency with pumping powers. When the excitation power increases to 983 mW, the QYs for detected 526 and 545 nm green, and 658 nm red emissions are up to 0.155 × 10⁻⁴, 1.405 × 10⁻⁴ and 0.255 × 10⁻⁴, respectively. Low phonon-energy Er³⁺/Yb³⁺ doped BZLFT glasses with intense luminous efficiency can work steadily at medium temperature range in view of its fast responses and high stability, moreover, a maximum sensitivity reaches 4.77 × 10⁻³ K⁻¹ at 587.5 K, which indicates that the BZLFT glass material has a good thermal sensitivity. The macroscopic quantization for UC photon generation and the exploration of maximum sensitivity value from Er³⁺ in high transparent fluorotellurite glasses provide a reliable reference for developing optical temperature-sensing materials.