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

A portable all-fiber thermometer based on the FIR technique in Er 3+ /Yb 3+ co-doped TeO 2 -WO 3 -La 2 O 3 -Na 2 O (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 Eu 3+ ions and Judd-Ofelt analysis of Er 3+ 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 Er 3+ /Yb 3+ 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. A portable all-fiber thermometer based on the fluorescence intensity ratio technique in Er 3+ /Yb 3+ co-doped TeO 2 -WO 3 -La 2 O 3 -Na 2 O (TWLN) glass fiber was designed and its temperature sensing performance was determined.