Spectroscopic study of Nd3+/Yb3+ in disordered potassium bismuth molybdate laser crystals

In this work we report the study of energy transfer between Nd3+ and Yb3+ ions in disordered K5Bi1−x−yNdxYby(MoO4)4 crystals (x = 0.01, 0.05, 0.1, 0.15, 0.2 and y = 0.1) at room temperature by using steady-state and time-resolved laser spectroscopy. The spectroscopic properties of Nd3+ and Yb3+ ions in these crystals make them suitable for efficient energy transfer because of the energy gap between the 4F3/2(Nd3+) and 2F5/2(Yb3+) levels which is around 300 cm−1. The transfer efficiency obtained from the lifetimes in the single doped and codoped samples reaches 77% for the highest Nd3+ concentration. The donor decay curves obtained under pulsed excitation have been used to establish the multipolar nature of the Nd3+ → Yb3+ transfer process and the energy transfer microparameter. The nonradiative energy transfer is consistent with an electric dipole–dipole interaction mechanism assisted by energy migration among donors. Back transfer from Yb3+ to Nd3+ is not observed at the Yb3+ concentration and temperature used in this work.