Analysis of the transparent-crystal ionization model developed by L. V. Keldysh

The goal of this paper is to clarify the degree of generality and the area of applicability of L. V. Keldysh's formula for the rate of laser ionization of transparent crystals. It discusses the physical model that forms the basis of Keldysh's calculations. According to this model, ionization is regarded as interband transitions between states whose perturbation is associated with oscillations of electrons in the first Brillouin zone under the action of the electric field of the. laser radiation. By analyzing this model, we determine the main restrictions on the applicability of the Keldysh formula, the most substantial of which are associated with fact that the band structure strongly affects the ionization rate. Using these results, the possibility of interpreting the experimental data on laser ionization and the breakdown of transparent solid media on the basis of the Keldysh formula is considered. (C) 2004 Optical Society of America.