Polymeric matrices for lasing dyes: Recent developments

An overview of recent results obtained by our group on the development of p olymeric solid-stale media incorporating either Rhodamine or Coumarin dyes is presented. The effect on the laser performance of the rigidity and visco elastic properties of the polymeric matrix has been investigated. Lasing ef ficiencies similar to those found in ethanolic solution, and improved photo chemical stability, as compared with that obtained in previous polymeric ma terials, were demonstrated for solid solutions of Rhodamine 6G (Rh6G) in ap propriate copolymer formulations of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA). Further improvements in photostability were obta ined when modified Rh6G molecules were copolymerized with HEMA and MMA. Whe n samples of this new highly homogeneous gain medium were placed in a rotat ing system, where the laser medium was scanned in a continuous way, a stabl e laser output with no sign of degradation after 500,000 shots was accompli shed for transversal pumping at 337 nm with 1.7 mJ pulses from a N-2-laser at 2 Hz repetition rate. The effect on laser operation of different polymerization methods, dye conc entration, and composition of the polymeric matrix was also investigated fo r Coumarin-doped gain media. Conditions were found that significantly impro ved both lasing efficiency and photostability in Coumarin 540A (C540A)-dope d 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.