Single- and multiple-shot laser-damage properties of commercial grade PMMA

In this paper, we describe a facility to study laser damage in plastics and present single- and multiple-shot bulk damage results obtained in commercial polymethylmethacrylate with 1.06-μm wavelength, 8-nsec FWHM, 45-μm spot diameter pulses. The measured single-shot peak fluence damage threshold is 41 J/cm2. Multiple-shot damage was studied at fluence levels as low as 6% of the single-shot damage threshold. Scattered collinear He–Ne laser light was found to be a very reliable indicator of damage, especially at the lower fluence levels. Histograms of damage statistics and 100× microscopy of the material after illumination with fewer than the critical numbers of pulses required for damage illustrate the cumulative nature of the damage process.