Multipath optical thermometry realized by electronic levels and Stark sublevels of Er3+
Guotao Xiang, Ming Xiong, Zhiyu Yang, Yongjie Wang, Yao Lu, Sha Jiang, Xianju Zhou, Li Li, Xiaojun Wang, Jiahua Zhang
Abstract
High-performance optical thermometer that can operate in the long-wavelength range of the second near infrared (1500 nm–1700 nm, NIR-IIb) biological window is in desperate need for bio-medical treatment. In this paper, a multipath temperature sensor Y 3 NbO 7 : Yb 3+ /Er 3+ with pure cubic phase is synthesized by the high temperature solid state method. Under the excitation of 980 nm wavelength, efficient green upconversion emission attributed to thermally coupled Er 3+ : 2 H 11/2 / 4 S 3/2 levels are found, through which an excellent temperature sensing properties are realized with the maximal absolute and relative sensitivity of approximately 0.54 % K −1 and 1.37 % K −1 as well as the minimal temperature resolution of about 0.024 K . More importantly, the sample exhibits remarkable temperature detection capacity in deep tissues, which is implemented by the thermally coupled Stark sublevels of Er 3+ : 4 I 13/2 locating just in the NIR-IIb sub-window. Thanks to this appropriate response wavelength range, the maximal penetration depth of the NIR-IIb optical thermometer in the biological tissues can reach up to 8 mm. All the findings indicate that the present sample is a supernormal multipath thermometric probe with detectability in the deep biological tissues.