Exploring promising up-conversion luminescence single crystal fiber in sesquioxide family for high temperature optical thermometry application

Abstract Facing the needs of optical thermometry application, the 0.5 at% Tm3+, 5 at% Yb3+ co-doped sesquioxide family (Lu2O3, LuScO3 and Sc2O3) single crystal fibers (SCFs) were successfully grown by the laser heated pedestal growth (LHPG) method. The Tm3+ and Yb3+ ions are uniformly distributed in the three fibers. The power dependent emission spectra with 980 nm excitation from 20 to 220 mW were investigated. There is a good linear relationship between the logarithm of emission intensity and the pumping power. In addition, the up-conversion luminescence (UCL) of the transitions of 3F2,3 →3H6 from 670 to 730 nm and 3H4 →3H6 from 750 to 850 nm of Tm3+ were systemically obtained with different temperature under a 980 nm laser. The maximum values of relative sensitivity of the Lu2O3, LuScO3 and Sc2O3 crystal fibers are 0.0056, 0.0180, 0.0067 K−1, corresponding to the temperature of 535, 323 and 427 K, respectively. The highest detection temperature of Lu2O3 and LuScO3 crystals was 973 K, while that of Sc2O3 crystal was up to 1073 K. Considering that Tm3+, Yb3+: Sc2O3 crystal still had high emission intensity at 1073 K, and the absolute sensitivity increases with increasing temperature, it was believed that the Sc2O3 crystal fiber was particularly suitable for higher temperature and sensitivity detection.