Up-conversion properties of Yb,Tb:YAG single crystals grown by the micro-pulling-down method
Résumé
Yb,Tb:YAG crystals with various Yb 3+ and Tb 3+ concentration were grown by the micro-pulling-down technique (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 Yb 3+ ions to one Tb 3+ ion. Under 4850 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 Tb 3+ ion to two Yb 3+ ions. The energy transfer processes from Yb 3+ ions to Tb 3+ ions were discussed, and the energy transfer efficiency was calculated. The results show that Yb,Tb:YAG crystal is promising for visible laser output when pumped by InGaAs laser diode (LD).
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