Prebreakdown excitation of crystals at double multiphoton resonance: III. Forbidden transitions

Abstract

Within the three-band model of a crystal, we calculated the probabilities of forbidden-allowed four-photon transitions between the valence band and the conduction band under conditions of two-photon resonance on the adjacent transition between two conduction bands. We show that the transformation of the electronic band spectrum under the action of high-power light of a prebreakdown intensity leads to a nonmonotonic dependence of the rate of photogeneration electron-hole pairs on the radiation intensity. We determined conditions under which a small change in the intensity in the range 1011–1013 W/cm2 leads to an increase in the generation rate of electron-hole pairs by more than an order of magnitude, which can cause an increase in the number of nonequilibrium carriers to values sufficient to trigger processes of destruction of the material.