LASER PERFORMANCE OF COUMARIN 540A DYE MOLECULES IN POLYMERIC HOST MEDIA WITH DIFFERENT VISCOSITIES - FROM LIQUID SOLUTION TO SOLID POLYMERMATRIX

Photophysical parameters and lasing properties of Coumarin 540A dye mo lecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylat e). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influe nce of the rigidity of the medium on the radiative processes. The phot odegradation mechanisms acting on the fluorophores are analyzed by fol lowing the dependence of laser induced fluorescence and laser output o n the number of pump laser pulses. The fluorescence redistribution aft er pattern photobleaching technique is used, and Fick's second law is applied to study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined. (C ) 1998 American Institute of Physics. [S0021-8979(98)01702-2].