Radiative and nonradiative transitions exhibited by Er3+ions in mixed yttrium-erbium aluminum garnets

An investigation was made of the contribution of radiative and nonradiative transitions to the deactivation of the upper laser levels 4S3/2, 4I11/2 and 4I13/2 of the Er3+ ion in mixed yttrium-erbium aluminum garnets. The optimal activator concentrations, ensuring minimum concentration quenching of the luminescence, were determined. A comparison of the Einstein coefficients, deduced from the corresponding integrated absorption coefficients, with the experimentally determined room-temperature lifetimes of the levels 4I11/2 and 4I13/2 established that the quantum efficiency of the 4I13/2 level was unity (to within the experimental error) and that of the 4I11/2 level did not exceed 0.017. However, the possibility of using high activator concentrations made the laser utilizing the 4I11/2–4I13/2 transition sufficiently efficient.