Einstein coefficients, stimulated emission cross sections, and absolute quantum efficiencies of luminescence from the metastable state 4F3/2 of Nd3+ in laser glasses and garnet crystals

Measurements were made of the Einstein coefficients of all the radiative transitions, stimulated emission cross sections σ_st and quantum efficiencies η of the luminescence from the metastable state ⁴F_3/2 of Nd³⁺ in several silicate and phosphate glasses and in garnet crystals. The quantum efficiency measurements were carried out by direct and indirect methods, the latter based on a comparison of the directly determined kinetics of the decay of the excited state with an exponential kinetics governed by the total Einstein coefficient of all the radiative transitions. The results obtained by these two methods were in good agreement. Hence, it was concluded that there was only a slight variation of the probabilities of radiative transitions between various activator centers whose excited-state energies were within an inhomogeneously broadened spectral profile. The values of η for the majority of glasses were in the range 0.3–0.7. The exception was the ED-2 glass (1 wt. % Nd₂O₃), for which (as for garnet crystals) the efficiency was η ~ 1. An analysis was made of the differences between our values of σ_st and those given in the literature for some types of glass.