Optical surface breakdown of alkali halide crystals by microsecond pulses from a wide-aperture CO2 laser

A study was made of the dynamics of temporal and spatial changes in the spectral characteristics of plasmas. A three-stage mechanism of the damage to surfaces of alkali halide crystals by microsecond pulses from a TEA CO₂ laser was proposed: breakdown initiation (at a distance of 3 — 5 mm from the surface with a time delay up to 1 μs relative to the leading edge of a laser pulse), evaporation (after a further delay of 3 — 5 μs), and interaction of the adsorbates with a plasma jet and with the laser radiation, as well as heating and cracking of a crystal by the UV plasma radiation.