Abstract

Nonequilibrium carrier distributions can be observed in semiconductors by monitoring the corresponding induced transparency on a femtosecond timescale. This bleaching occurs since, because of the Pauli exclusion principle, optical transitions cannot occur for final states occupied by previously created carriers. Just after the excitation by a short pump pulse, the nonthermal carrier distribution reflects the excitation energy profile. Experimentally, this appears as a spectral hole-burning in the interband absorption. The bleaching does not remain peaked at the excitation energy since different interactions tend to rapidly redistribute the carriers into thermalized distribution.

© 1992 The Author(s)