Polymeric Matrices for Lasing Dyes: Recent Developments

An overview of recent results obtained by our group on the development of polymeric solid-state media incorporating either Rhodamine or Coumarin dyes is presented. The effect on the laser performance of the rigidity and viscoelastic properties of the polymeric matrix has been investigated. Lasing efficiencies similar to those found in ethanolic solution, and improved photochemical stability, as compared with that obtained in previous polymeric materials, were demonstrated for solid solutions of Rhodamine 6G (Rh6G) in appropriate copolymer formulations of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA). Further improvements in photostability were obtained when modified Rh6G molecules were copolymerized with HEMA and MMA. When samples of this new highly homogeneous gain medium were placed in a rotating system, where the laser medium was scanned in a continuous way, a stable laser output with no sign of degradation after 500,000 shots was accomplished for transversal pumping at 337 nm with 1.7 mJ pulses from a N2-laser at 2 Hz repetition rate. The effect on laser operation of different polymerization methods, dye concentration, and composition of the polymeric matrix was also investigated for Coumarin-doped gain media. Conditions were found that significantly improved both lasing efficiency and photostability in Coumarin 540A (C540A)-doped polymeric matrices. Insight into the main photodegradation mechanisms of this dye was provided by the study of fluorescence and lasing properties of a number of C540A solutions with increased viscosity, from liquid solution to solid polymer matrix.