A portable all-fiber thermometer based on the fluorescence intensity ratio (FIR) technique in rare earth doped TeO2–WO3–La2O3–Na2O glass

Abstract

A portable all-fiber thermometer based on the FIR technique in Er³⁺/Yb³⁺ co-doped TeO₂–WO₃–La₂O₃–Na₂O (TWLN) glasses was designed and its temperature sensing performance in the temperature range of 293–569 K was determined in detail. The high glass transition temperature (T_g = 439 °C) of TWLN glass contributes to broadening the range of temperature measurement. The spectroscopic analysis of Eu³⁺ ions and Judd–Ofelt analysis of Er³⁺ ions reveal that the rare earth ions are situated in a low symmetry environment in TWLN glass, which suggests that a large FIR change and high temperature sensitivity are expected. Intense green upconversion emission in Er³⁺/Yb³⁺ co-doped TWLN glass fiber was easily observed under 980 nm excitation at a low pumping power (1.4 mW). The maximum temperature sensitivity of the portable all-fiber thermometer reached 86.7 × 10⁻⁴ K⁻¹ at 553 K. Experimental results showed that the absolute errors were around ±1 K within the temperature range from 285 to 563 K.