Optical strength of window materials in wide-aperture repetitively pulsed CO2 lasers

It was established experimentally that irradiation of ionic single crystals by a series of microsecond pulses from a TEA CO2 laser, of 1-15 s duration at a repetition rate in excess of 100 Hz, caused damage at subthreshold intensities as a result of gradual accumulation of thermally induced internal stresses. When the series of pulses were shortened, the dominant damage mechanism was that typical of pulsed irradiation: breakdown at absorbing micro-inhomogeneities.