Stimulated-emission cross section and fluorescent quantum efficiency ofNd3+in yttrium aluminum garnet at room temperature

The stimulated-emission cross sections and fluorescence branching ratios for the principal fluorescence transitions of YAG:Nd emanating from the $^{4}F_{\frac{3}{2}}$ state have been measured at room temperature. The peak cross section of the well-known 1064.2-nm laser line is here found to have a value of 4.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$ ${\mathrm{cm}}^{2}$. Since the cross sections reported here are inconsistent with the generally accepted value of near unity for the radiative quantum efficiency $\ensuremath{\eta}$ of the $^{4}F_{\frac{3}{2}}$ state the quantity $\ensuremath{\eta}$ has been measured directly. A value of 0.56\ifmmode\pm\else\textpm\fi{}0.11 is found for $\ensuremath{\eta}$ which is consistent with the observed fluorescence lifetime of the $^{4}F_{\frac{3}{2}}$ state and the measured cross sections.