Abstract

The results of the long term investigation (see, e.g. review [1] ) of the wide gap insulating crystals optical spectra have shown that their fundamental absorption edge is formed by the exciton states with a large oscillator strength. On the other hand, it is well-known that just the excitons play the important role in the manifestation of the nonlinear properties in the optical spectra of the huge number of the nonmetallic compounds. Particularly, on the example of the ionic semiconductors it was shown (see, e.g. reviews [2; 3]) that the excitons appoint the main channel of electronic transitions in the stimulated emission. Namely this circumstance provides the high energetical yield of the coherent emission per unit volume of the matter.

© 1990 Optical Society of America