Ultraviolet radiation, in a band of wavelengths near 300 nm, produced by the flashlamps used to pump the ruby rod, is responsible for nearly all the photochemical decomposition (irreversible bleaching) of methanolic solutions of cryptocyanine used as passive shutters (Q-switches) in high-peak-power ruby lasers. The laser beam itself has little or no irreversible effect upon cryptocyanine.
Roberta A. Hollier and James D. Macomber, "Light Source Responsible for the Deterioration of Cryptocyanine Q-Switches," Appl. Opt. 11, 1360-1364 (1972)