Some aspects of the initial stage of the development of laser damage in polymethylmethacrylate

An investigation was made of the influence of microstructure defects in polymethylmethacrylate (PMMA) on the laser damage threshold. It was found that microstructure defects in PMMA reduced the threshold by a factor of 4–6 compared with the threshold of the monomer. The damage threshold was determined in the course of polymerization of PMMA and it was found that the threshold decreased abruptly by a factor of 3–4 during the last stage of polymerization when the degree of conversion was 90%. It was likely that microstructure defects, which reduced the optical strength of the material, formed at this stage. An investigation was made of the appearance of defects during laser irradiation. The appearance of defects was accompanied by luminescence. Two possible mechanisms of the initial stage of the laser damage in methylmethacrylate and PMMA were suggested.