Photophysical characteristics of coumarin 485 dye doped poly(methyl methacrylate) modified with various additives

The influence of medium on the photophysical properties of a fluorinated co umarin (coumarin 485, C485) is studied in detail. The absorption and fluore scence characteristics of coumarin 485 dye doped poly(methyl methacrylate) modified with various additives (1,4-dioxane, chloroform, n-butyl acetate, acetonitrile and ethanol) are studied and the results are compared with the respective liquid mixtures. The fluorescence lifetime, fluorescence quantu m yield, radiative and the non-radiative decay constants of C485 in polymer and corresponding monomer compositions are obtained. The gain characterist ics of C485 in various modified poly(methyl methacrylate) (MPMMA) matrices are studied at various nitrogen laser powers in a transverse pumping config uration and the results are compared with the gain characteristics in the c orresponding liquid mixtures. It is found that the gain of C485 in MPMMA in creases with the increase in the dielectric constant of the medium while in the liquid medium, the reverse effect is observed. It is also found that t he gain coefficient of C485 in a solid matrix shows 90% reduction when comp ared to the liquid medium. The photobleaching effect of this dye is also st udied for a fixed nitrogen laser power and it is found that the photobleach ing effect decreases with the increase in the dielectric constant of the me dium. A significant improvement in the photostability was achieved from cou marin 485 doped PMMA modified with ethanol. The number of pumping pulses ne eded for 80% reduction of the initial output is 13 600 pulses for the input power of 10 kW and the repetition rate of 2 Hz.