Luminescence Thermometry Based on Time Gates: Highly Sensitive Approach for Real-Time Sensing and Imaging

Undoubtedly, one of the most significant advantages of luminescence thermometry is its ability to be used not only for spot temperature measurements but also for imaging temperature changes. Among the commonly proposed approaches, luminescence thermometry based on luminescence kinetics holds particular promise. However, most thermometric studies rely on the analysis of luminescence decay profiles, a method that significantly hinders, if not entirely precludes, real-time thermal imaging. In this Letter, we propose an alternative approach based on the luminescence intensity ratio integrated over two temporal gates. Tests conducted on two representative phosphors, Ba₂LaNbO₆:1%Mn⁴⁺ and Ca₂LaNbO₆:1%Mn⁴⁺, demonstrate that the proposed method not only enables thermal imaging but also achieves substantially higher relative sensitivity, reaching <i>S</i>_R = 17.1% K^-1 for Ba₂LaNbO₆:1%Mn⁴⁺ and <i>S</i>_R = 9.4% K^-1 for Ca₂LaNbO₆:1%Mn⁴⁺, compared to the conventional lifetime-based approach (<i>S</i>_R = 4.2% K^-1 for Ba₂LaNbO₆:1%Mn⁴⁺ and <i>S</i>_R = 1.2% K^-1 for Ca₂LaNbO₆:1%Mn⁴⁺). Furthermore, the careful selection of gate lengths allows optimization of the thermometric performance of the proposed luminescent thermometers. This approach enables expansion of the thermal operating range at the cost of relative sensitivity, providing versatility to adapt the thermometer for specific applications.