Er3+/Yb3+/Ho3+ tri-doped no-core fiber temperature sensor based on fluorescence intensity ratio technology: towards high stability and accurate measurements

Abstract

In this paper, the green upconversion (UC) fluorescence emission from Er3+/Yb3+/Ho3+ tri-doped tellurite glass is investigated for temperature sensing. The doping of Ho3+ ions not only enhances the chance of energy level transition but also avoids the influence of the thermal effect caused by the proximity of 2H11/2 and 4S3/2 energy levels. The luminescence characteristics at different Yb3+ and Ho3+ ion concentration doping molar ratios were investigated, and the strongest luminescence characteristics were exhibited when the Yb3+ ion concentration was at 5 mol% and Ho3+ at 0.2 mol%. Based on this, a tri-doped TeO2-ZnO-Bi2O3 (TZB) no-core fiber was fabricated and connected with multimode fibers (MMFs) to form a temperature sensor. The temperature sensing performance of the tri-doped TZB temperature sensor was evaluated in detail over the temperature range of 255–365 K. The repeatability and stability of the temperature sensor was experimentally verified. The Er3+/Yb3+/Ho3+ tri-doped sensor can be used for noninvasive optical temperature sensing in the fields of environmental monitoring, biological sensing, and industrial process temperature control, etc.