Temperature sensor based on ladder-level assisted thermal coupling and thermal-enhanced luminescence in NaYF4: Nd3+

NaYF4: Nd3+ microprisms were synthesized by a hydrothermal method. The bands of near-infrared (NIR) luminescence originating from the F-4(3/2), F-4(5/2) and F-4(7/2) levels of Nd3+ ions in NaYF4: Nd3+ microcrystals were measured under 574.8 nm excitation at various temperatures from 323 to 673 K. The fluorescence intensity ratios (FIRs) between any two of the three bands change monotonically with temperature and agree with the prediction assuming thermal couplings. A large relative temperature sensitivity of 1.12% K-1 at 500K is reached with the FIR of 4F(7/2) to F-4(3/2) levels. In addition, anti-Stokes fluorescence from F-4(5/2) level (740 nm) and F-4(5/2,7/2) levels (740 nm and 803 nm) of Nd3+ ions was studied meticulously under 793.8 nm and 864.2 nm excitations, respectively. The intensities were shown to be greatly enhanced as temperature increases, and the 740 nm band from F-4(7/2) level at 458 K increases in intensity by 170 fold relative to that at 298 K under the 793.8 nm excitation. (C) 2014 Optical Society of America