Absorption intensities and emission cross sections of principal intermanifold and inter-Stark transitions of $Er3+(4f11)$ in polycrystalline ceramic garnet $Y3Al5O12$

A comparative spectroscopic study is performed on $Er3+(4f11)$ ions doped in polycrystalline ceramic garnet $Y3Al5O12$ (YAG) and single-crystal laser rod, both containing nominal 50 at. % of $Er3+$⁠. The standard Judd–Ofelt (JO) model is applied to the room-temperature absorption intensities of $Er3+(4f11)$ transitions in both hosts to obtain the phenomenological intensity parameters. These parameters are subsequently used to determine the radiative decay rates, radiative lifetimes, and branching ratios of the $Er3+$ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds $LJ2S+1$ of $Er3+(4f11)$ in these garnet hosts. The emission cross sections of the intermanifold $Er3+I13∕24→I15∕24$ (1.5 μm) transition as well as the principal inter-Stark transition $Y1→Z4$ (1550 nm) within the corresponding multiplet manifolds have been determined. The room-temperature fluorescence lifetimes of the $I13∕24→I15∕24$ (1.5 μm) transition in both polycrystalline ceramic and single-crystal YAG samples were measured. From the radiative lifetimes determined from the JO model and the measured fluorescence lifetimes, the quantum efficiencies for both samples were determined. The comparative study of $Er3+(4f11)$ ions performed suggests that polycrystalline ceramic YAG is an excellent alternative to single-crystal YAG rod for certain applications.