Interband phototransitions involving free electrons: Part II. Crystals with an indirect band gap
Nonlinear absorption of laser radiation with a photon energy lower than the indirect band gap of crystal has been considered. It is shown that, as in the case of direct-gap materials, single-photon resonance at the transitions between two conduction bands even at radiation intensities j ∼ 105–106 W/cm2 yields a range of j values where optical absorption and concentration of nonequilibrium electron-hole pairs increase very sharply with an increase in j.
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