Abstract

Free-exciton resonances in semiconductors cannot be treated as bare two-level systems because Coulomb interaction and correlation/ exchange effects between the carriers substantially modify the optical Bloch equations that describe the behavior of a two-level system under the influence of an external light field. The semiconductor Bloch equations (SBEs) give a more realistic description of the dynamic response of the system on ultrafast time scales. Therefore, the coherent transients known from two-level systems in atomic physics have been found to be substantially modified in semiconductors. Whereas self-induced transparency (SIT) on bound excitons,¹ which are known to behave as atomiclike two-level systems, has been found, the question whether SIT could also appear on a free-exciton resonance is still subject of controversial discussions. We addressed this problem in a combined theory-experiment study.

© 1998 Optical Society of America