Up-conversion properties of Yb,Tb:YAG single crystals grown by the micro-pulling-down method

Yb,Tb:YAG crystals with various Yb3+ and Tb3+ concentration were grown by the micro-pulling-down method (μ-PD). The absorption spectra, fluorescence spectra and fluorescence decay curves of Yb,Tb:YAG crystals were measured at room temperature. Under 980 nm excitation, Yb,Tb:YAG crystals exhibited intense visible up-conversion luminescence due to the cooperative energy transfer from two Yb3+ ions to one Tb3+ ion. Under 485 nm excitation, Yb,Tb:YAG crystals yielded near-infrared down-conversion emission, ascribing to the cooperative absorption of pumping photons and cooperative energy transfer from one Tb3+ ion to two Yb3+ ions. The energy transfer processes from Yb3+ ions to Tb3+ ions were discussed, and the energy transfer efficiency was calculated. Based on studies of the obtained results, Yb3+/Tb3+ co-doped YAG crystal shows promising potential for sensing, volumetric displays, optical data storage, light emitting diodes.