Optical temperature sensing characteristics of Sm3+ doped YAG single crystal fiber based on luminescence emission

A series of YAG: x mol%Sm3+ single crystal (SC) materials, in which x is 0.3, 0.5, 1, 2, respectively, have been synthesized through laser heated pedestal growth (LHPG) method. The down-conversion luminescence properties of prepared fluorescent materials were investigated under a 405 nm laser. According to the results, 0.5 mol% was selected as the optimal doping concentration, and the integrated YAG single crystal fiber (SCF) with end Sm3+ doped was further fabricated. Then the optical temperature sensing characteristics were studied by the technique of the fluorescence intensity ratio (FIR) in detail. It shows that 4F3/2 and 4G5/2 of Sm3+ ions are thermally coupled energy levels. The FIR of the 4F3/2/4G5/2 → 6H5/2 increases monotonously as temperature rises, and its temperature measurement range can be extended to 1178 K. The maximum absolute sensitivity and maximum relative sensitivity are 3.046 × 10−4 K−1(1129 K) and 5.033 × 10−3 K−1 (500 K), respectively. Additionally, the FIRs of various emission bands from 4G5/2 → 6H5/2, 7/2 and the FIR of the emission sub-bands from 4G5/2 → 6H9/2 exhibit temperature dependence in 303–1028 K and 303–878 K, respectively. These results indicate that YAG: Sm3+ SC is a very promising high-temperature sensing material.