Investigation of the interactions between dissimilar ions in (Er, Nd):Y_3Al_5O_12

Abstract

Unusual fluorescence decay properties of both Er3+ and Nd3+ ions in (Er, Nd):YAG are reported. Studies reveal that the cross-relaxation-type ion–ion interactions involving Er3+ and Nd3+ ions are responsible. A rate-equation analysis is used to evaluate the interaction strengths of all the proposed processes. The rate-equation calculation does not fully explain the nonexponential nature of the measured fluorescence decay function of the 4F3/2 Nd3+ ions. As a result, the theory for donor–acceptor energy transfer processes, based on the inverse-power transfer rate model, is adopted to study the mechanism of the interactions between Er3+ and Nd3+ ions that result in the drastically altered fluorescence decay of is Nd3+ ions. It is found that the mechanisms governing the energy transfer processes have functional forms different from those for the commonly encountered electric multipolar interactions. The interaction strengths are evaluated by least-squares fitting of the theory to the experimental data. Effects of the ion–ion interactions on lasing properties of the (Er, Nd):YAG are also discussed.