Abstract

The electrons in crystals are distributed in energy bands rather than in sharp levels as in atoms or molecules. In semiconductors optical transitions across the band gap generate electrons in the conduction band and holes in the valence bands. Because of the rapid scattering of the excited carriers in the bands by carrier-phonon and carrier-carrier scattering, the interband polarization decays within ten to a few hundred femtoseconds. The study of coherent optical phenomena in semiconductors for the intrinsic band-to-band transitions needs femtosecond spectroscopy.

© 2000 Optical Society of America