Electron avalanche breakdown by laser radiation in insulating crystals

Recent experimental investigations into laser−induced damage in the alkali halides have indicated that the damage is due to avalanche breakdown in its dc limit. Numerical computations for NaCl have been carried out that show that the ionization rate can be accurately computed by a classical diffusion or Fokker−Planck approximation to the Boltzmann equation for ionization rates on the order of 1012 sec−1. For hot electrons it is necessary to add a contribution to the collision frequency that is due to the deformation potential in order to explain the dc character of breakdown by 1.06−μm radiation.