LASER-DYE STABILITY .4. PHOTODEGRADATION RELATIONSHIPS FOR BICYCLIC DYES IN ALCOHOL SOLUTIONS

Changes in the absorption of a dye laser solution are examined after excitation with a xenon flashlamp. It is found that the rate of bleaching as a function of the total input energy of coumarin or quinolone dyes in ethanol increases in direct proportion to the dye concentration. This relationship suggests that the dye reacts with a photoproduct of the solvent rather than being directly decomposed by the xenon flash. We have measured the conversion of the dye to form products, P, absorbing at the lasing wavelength. Results correspond to the dye reacting with a precursor of P to form either insoluble products or ones not absorbing at the lasing wavelength. Thus larger total amounts of bleached dye do not proportionately increase P, and hence do not proportionately inhibit lasing. Furthermore, we find that P increases with the total input energy fairly independent of the rate of bleaching for a given bicyclic dye in an alcohol solution. © 1978 Springer-Verlag.