Measurement of the Laser Transition Cross Section forNd+3in Yttrium Aluminum Garnet

This paper reports measurements of the room-temperature laser transition cross section of ${\mathrm{Nd}}^{+3\mathrm{}}$ in yttrium aluminum garnet at 1.06 μ. One method used is based on the measured upper-state lifetime and a determination of the fluorescence branching ratio for this state. The value thus determined is 3.5×${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$. The second method involves measurement of the ratio of fluorescent intensities from the upper laser level to the ground state and to the lower laser level, and measurement of the cross section in absorption of the transition which involves the ground state. The second method yields a value of 2.7×${10}^{-19\mathrm{}}$ ${\mathrm{cm}}^2$. The difference represents the contribution of fluorescence to high-lying levels (not included in the determination of branching ratio) and nonradiative transitions. The probable experimental accuracy in both methods is ±15%.