Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters

Erbium (Er)-doped fluoride crystals (YLF, BYF, CaF2, etc.) are well-known as active media for solid-state lasers emitting in IR and VIS spectral domains, and as materials for efficient near-IR to VIS upconversion. In this paper, we report on the study of conversion of IR light from an ∼1.5 μm spectral region to an ∼1 μm spectral domain in low-phonon RE-doped fluoride crystals CaF2 (RE=Er3+ Yb3+). Energy transfer processes taking place at selective pulsed and CW laser excitation are investigated experimentally. It is shown that in the CaF2:RE crystals efficient conversion of IR radiation from the ∼1.5 μm region to the ∼1 μm region occurs, and these crystals are perspective for using in spectral converters for enhancing solar cell efficiency.