Emission from the high lying excited states of Ho3+ ions in YAP and YAG crystals

The near UV and visible emissions of Ho3+ in YAP and YAG are investigated after selective one photon pumping of the 3D3 and 5S2 manifolds. The fluorescence decays of Ho3+ ions after pulsed excitation are measured as a function of temperature and holmium concentration. The shortening and non-exponentiality of the decays, observed with increasing activator concentrations, are indications of cross-relaxation (CR) among the Ho3+ ions. The CR schemes are proposed for both emitting 3D3 and 5S2 manifolds and the values for the transfer rates are experimentally determined and compared to the Inokuti–Hirayama theory. Mechanisms responsible for the temperature quenching are studied.