Passive Q switching of a flash-lamp-pumped ruby laser has been demonst
rated with a Dy2+:CaF2 saturable absorber at room temperature. Typical
ly a single Q-switched pulse of 4.5 mJ and 94 ns was observed. At 694
nm, the ground-state absorption cross section and excited-state absorp
tion cross section of the Dy2+:CaF2 absorber were found to be 1.2 x 10
(-18) cm2 and 0.9 x 10(-18) cm2, respectively, with a four-level slow-
relaxing saturable-absorber model.