A three-mode temperature sensing based on UC luminescence of Er:PbF2 crystal

Optical temperature sensor, especially the temperature sensor made based on fluorescence intensity ratio (FIR) technology, have numerous applications in temperature detection. However, most of these sensing materials are phosphors, which still face challenges in maintaining their chemical stability. In contrast, crystal materials exhibit superior thermal stability and fluorescence stability. The temperature sensing characteristics of Er: PbF2 single crystal material were studied by the three modes temperature dependence curve. Excellent relative sensitivity and absolute sensitivity were obtained on FIR between two non-thermally coupled energy levels (non-TCEL: I(4F9/2)/I(4S3/2)) and two thermally coupled energy levels (TCEL: I(2H11/2)/I(4S3/2), and I(4S3/2)/I(4S3/2)) of Er3+ ions when excited by a 980 nm LD. Futhermore, with the increase of temperature, the luminescence emission color of the Er: PbF2 single crystal varied from green to yellow-orange. These discoveries suggest that the Er: PbF2 single crystal could serve as an excellent sensing medium for optical temperature sensors.