Photothermal characterization and stability analysis of polymeric dye lasers

The millisecond heat dissipation of pump energy in polymeric, solid-state dye lasers has been studied with photothermal deflection spectroscopy (PTDS) to determine the contribution of that process to photodegradation of the active material. The samples were solutions of Rhodamine 6G in 2-hydroxyethyl methacrylate copolymerized with various amounts of methyl methacrylate or ethylene glycol dimethylacrylate to change the microstructure properties of the matrix. Values of the thermal diffusivity measured with PTDS were in the range 0.6-1.1 x 10(-3) cm(2) s(-1) for all the compositions studied here. A comparison of these values with previous optical data on lasing efficiency and photostability for the same samples indicates that the macroscopic rate of thermal diffusion is not the key factor that limits the efficiency and stability of these lasers, at least for low pump repetition rates (<1 Hz).