Z-scan measurement of the ground and excited state absorption cross sections of Cr/sup 4+/ in yttrium aluminum garnet

Z-scan measurements of the ground and excited state absorption cross sections of Cr/sup 4+/-doped yttrium aluminum garnet are reported. These quantities are found to depend on crystal preparation but are independent of temperature from -60/spl deg/C to 98/spl deg/C. Their ratio is shown to weakly determine the energy output of a passively Q-switched Nd:glass laser using this material as the saturable absorber.