Title: Photostability and beam strength of polyurethane matrices for active element of solid-state dye lasers

Abstract

Among the main requirements, which should be met by the polymer matrices in dye laser solid-state elements, their photostability and beam strength are crucial factors. Here photostability is understood as polymer resistance to photo oxidation and photochemical destruction, and beam strength means ability of the material to withstand irreversible changes of its optical parameters and retain integrity under strong optical irradiation (in particular, by a laser), including stability to local overheating. The use of polymer matrices based on polyurethane elastomers allows providing stable operation of dye lasers due to high segmental mobility and effective control of properties using different components and various curing conditions. Effect of variation of diisocyanate and glycol polyurethane components on photostability and beam strength of the polyurethane matrix have been investigated as well as the methods of that characteristics evaluation. This work presents a comparative analysis of photo oxidation destruction characteristics for different PU polymers, and their beam strength parameters, obtained by various methods (IR-spectroscopy, dynamic mechanical analysis (DMA), paramagnetic probe and laser experiments). Elastic characteristics in a wide temperature range and high beam strength of the obtained polyurethanes cause prospects of these materials for the applications as efficient solid-state laser elements. The observed good agreement in the correlations between the polyurethane chemical structure and changes in the modulus of elasticity, probe relative penetrability, probe correlation time, amount of OH-containing radicals formed after irradiation, and also the measured values of the single-pulse laser damage threshold, allows to predict stability of further developed polyurethane-based materials under continuous laser operation.