Spectroscopy of ${\mathrm{Y}}_3$${\mathrm{Al}}_5$${\mathrm{O}}_{12}$:${\mathrm{Nd}}^{3+}$ under high-power, picosecond-pulse excitation

High-power, picosecond-pulse excitation was used to study the dynamics of the pumping and decay processes in ${\mathrm{Y}}_3$ ${\mathrm{Al}}_5$ ${\mathrm{O}}_{12}$:${\mathrm{Nd}}^{3+}$. The observed fluorescence spectral lines are assigned to transitions from three different metastable states excited by both single-photon and two-photon absorption. The branching ratios, lifetimes, and quantum efficiencies of the metastable states are obtained from the data as well as the two-photon absorption cross sections. The results provide useful information concerning ultraviolet pumping efficiencies of the Nd-YAG (Nd-doped yttrium aluminum garnet) laser transition and the $5d-4f$ nonradiative decay rate for this material. In addition, the time-resolved spectroscopy method employed here is shown to be an extremely sensitive technique for obtaining two-photon absorption cross sections.