Interaction Between Intense Optical Radiation and Matter

The report describes a study of the nonlinear absorption properties of a number of the organic dye molecules which have been widely used in conjunction with ruby lasers. The dominant characteristic of this nonlinear behavior is a reduction in the optical transmission of a dye sample when irradiated with intense laser light. The three dye molecules studies are cryptocyanine, metalfree phthalocyanine, and chloroaluminum phthalocyanine, which were dissolved in a variety of solvents. The primary photophysical processes of polyatomic molecules are discussed. Several excited-state lifetime of the three molecules have been determined experimentally. The saturation of molecular absorption for these three molecules is analyzed on the basis of a rate equation approach to a simple three-level model plus excited-state absorptions. The general characteristics of dye Q-switched laser pulse evolution are also discussed and experiments are described which were performed to study the nature of the spectral hole-burning responsible for frequency-locking between different lasers. Also research on photon-induced breakdown of gases due to inverse Bremsstrahlung is very briefly summerized. Sponsored in part by DARPA.