Thermosensitive Tm3+/Yb3+ co-doped oxyfluorotellurite glasses - spectroscopic and temperature sensor properties

Oxyfluorotellurite (65-x)TeO2-20ZnF(2)-12PbO-3Nb(2)O(5)-xTm(2)O(3) (x = 0.5, 2 and 5) and (65-x-y)TeO2-20ZnF(2)-12PbO-3Nb(2)O(5)-xTm(2)O(3)-yYb(2)O(3) (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were manufactured. Glass thermal stability was examined by means of differential thermal analysis (DTA) and some thermal stability criteria Delta T, H' and S were determined. Absorption spectrum was utilized to prepare Judd-Ofelt (J-O) calculations and consequently oscillator strengths, intensity parameters Omega 2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were estimated. Emission spectra and luminescence decay curves were measured as a function of temperature in the 300-625 K range. Based on the upconversion luminescence of Tm3+ the optical temperature sensor qualities have been evaluated for Tm3+/Yb3+ co-doped sample. The fluorescence intensity ratio (FIR) between transitions 700 nm (Tm3+:F-3(2,3) -> H-3(6))/800 nm (Tm3+:H-3(4) -> H-3(6)) for 975 nm excitation and 700 nm (Tm3+:F-3(2,3) -> H-3(6))/470 nm (Tm3+:(1)G(4) -> H-3(6)) for 803 nm excitation were determined and an adequate relative thermal sensitivity S was estimated. The significant value of relative thermal sensitivity 1.12 %K-1 was determined when NIR Yb3+ and Tm3+ emission bands were analyzed, however. Effective emission cross section was calculated for F-3(4) -> H-3(6) potential laser transition of thulium around 1.9 mu m in single-doped Tm3+ glass. Furthermore, effect of temperature on down-converted and up-converted thulium and ytterbium emission and on relaxation dynamic of involved excited states was studied in details. (C) 2020 Elsevier B.V. All rights reserved.