Abstract
The advantages of a polyurethane matrix over other polymers, which are widely used as active media for dye lasers, are analysed. This matrix exhibits the photostability, service life, radiation resistance, conversion efficiency, and homogeneity of the dye distribution that surpass these properties for active media based on polyurethane acrylate, which has close physical and operation properties. These advantages result not only from the milder polymerisation conditions but also from a lower probability of the formation of ion pairs and dye aggregates. A substantial suppression of these processes in polyurethane is explained by its greater polarity and solvation ability compared to polyurethane acrylate.