Condensed-Matter Spectroscopy

Optics and Spectroscopy

, Volume 113, Issue 4, pp 376-382

First online:

Interband phototransitions involving free electrons: I. Crystals with a direct band gap

  • E. Yu. PerlinAffiliated withCenter of Information Optical Technologies, St. Petersburg State University of Information Technologies, Mechanics, and Optics Email author 
  • , A. V. IvanovAffiliated withCenter of Information Optical Technologies, St. Petersburg State University of Information Technologies, Mechanics, and Optics
  • , A. A. PopovAffiliated withCenter of Information Optical Technologies, St. Petersburg State University of Information Technologies, Mechanics, and Optics

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Abstract

Nonlinear absorption of laser radiation with a photon energy exceeding the half-width of the direct band gap of crystal but lower than its width has been considered. It is shown that, in the case of singlephoton resonance at transitions between two conduction bands, even at radiation intensities j ∼105–106 W/cm2, there is a range of j values where the optical absorption and concentration of nonequilibrium electron-hole pairs sharply increase with an increase in j. The transition of the material between states with different optical and electric properties occurs for few nanoseconds.