Optical spectroscopy of heavily Ho3+-doped BaY2F8 crystals

The ultraviolet, visible, and near IR (0.8–2.4 μm) luminescence spectra of BaY2F8 single crystals heavily doped with Ho3+ ions (10 and 30 mol%) have been investigated at room temperature and 12 K, together with the luminescence decay curves (up to 300 μs) of the visible emission. Excitation in the visible region gives rise to very strong emission bands originating from the first 5I7 level and located around 2070 nm. However the 5I7 emission is not observed upon excitation at wavelengths shorter than 300 nm. The inter-ionic processes are found to shorten the decay times of the levels emitting in the visible region with respect to the corresponding radiative lifetimes.