A high-precision thermometry strategy by replacing the infrared with visible light for detection
Lixin Peng, Feng Qin, Changwen Wang, Leipeng Li, Zhiguo Zhang
Abstract
We have developed a high-precision thermometry strategy based on 4 I 9/2 – 4 I 15/2 ( I 800 nm ) and 4 S 3/2 – 4 I 15/2 ( I 551 nm ) transitions of Er 3+ , after replacing the measurement of the 4 I 11/2 – 4 I 15/2 ( I 1000 nm ) transition with the 4 S 3/2 – 4 I 15/2 transition, i.e., using visible light for detection instead of infrared. Through rate equation model analysis, (I 1000 nm ) 2 and I 551 nm can be substituted for each other under certain conditions. Further, because the 4 I 9/2 and 4 I 11/2 levels of Er 3+ are thermally coupled, a new idea of ratiometric thermometry is proposed based on the ratio of ( I 800 nm ) 2 and I 551 nm , which has the advantages of anti-interference of excitation light source fluctuation and background-free detection. The feasibility of the idea was verified by researching the power-dependent emission spectra at different temperatures and temperature-dependent emission spectra of a CaWO 4 :Er 3+ ,Yb 3+ sample under 980 - nm laser excitation. The maximum relative sensitivity for the new ratiometric thermometry reaches up to 7.4% K −1 and the optimal temperature uncertainty calculated is 0.03 K at 303 K. This study provides guidance for solving the problem of a weak response of an infrared detector.