Up-converted emission in Pr3+-doped fluoride nanocrystals-based oxyfluoride glass ceramics

Red-to-blue up-converted emission has been studied for Pr3+-doped fluoride nanocrystals-based oxyfluoride glass ceramics. Emission by the P-3(0)-H-3(4) transition has been observed upon excitation of the D-1(2) manifold. The concentration. wavelength and flux dependence of the up-conversion have been investigated at different temperatures from 1.5 K at high spectral resolution. Excitation spectra indicate that the most efficient excitation is at 591.6 nm, which corresponds to the transition of D-1(2) (II), the second-lowest level of the D-1(2) manifold. The intensity of the blue emission shows a quadratic dependence on the incident flux. The dynamical processes of this up-conversion have also been examined. Suggesting that the energy-transfer process is responsible for the up-converted emission. The different spectroscopic features between nanocrystals and bulk crystals have been characterized, indicating that the local temperature in the nanocrystals is higher than that in bulk crystals due to the lower thermal conductivity of the glass matrix. (C) 2004 Elsevier B.V. All rights reserved.