Nd3+ --> Yb3+ energy transfer in the YAl3(BO3)4 nonlinear laser crystal

The main properties of the Nd3+→Yb3+ ( 4F3/2, 2F7/2→4I 9/2, 2F5/2) energy transfer in yttrium aluminum borate nonlinear laser crystal have been studied. This host has been found especially suitable for efficient Nd3+→Yb3+ energy transfer because of the good matching between phonon energy and the 4F3/2(Nd3+)-2F7/2(Yb 3+) energy gap (≅1000 cm-1). Energy-transfer probabilities in excess of 65% have been obtained for a Nd3+ (10 at. %) and Yb3+ (5 at. %) codoped sample. The influence of both crystal temperature and Nd3+ concentration on the transfer probability has been investigated. In the 15-350 K range the Nd3+→Yb 3+ energy-transfer efficiency increases with temperature, whereas for crystal temperatures above 350 K the Nd3+←Yb3+ back transfer is activated, leading to a decrease in the effective Nd 3+ →Yb3+ energy-transfer probability. The analysis of the decay curves obtained after pulsed excitation has been used to determine the multipole character of the Nd3+-Yb3+ interaction. The donor-acceptor energy-transfer microparameter was determined [CDA (Nd3+→Yb3+)≅ 18×10-39 cm 6/s], and compared to those obtained for other Nd 3+-Yb3+ co-doped materials.