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

Red-to-blue up-converted emission has been studied for Pr ³⁺-doped fluoride nanocrystals-based oxyfluoride glass ceramics. Emission by the ³P₀-³H₄ transition has been observed upon excitation of the ¹D₂ manifold. The concentration, wavelength and flux dependence of the up-conversion have been investigated at different temperatures from 1.5K at high spectral resolution. Excitation spectra indicate that the most efficient excitation is at 591.6nm, which corresponds to the transition of ¹D₂ (II), the second-lowest level of the ¹D₂ 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.