Abstract

The nonequilibrium dynamics of photoexcited semiconductors occurs on ultrafast time scales and is initially governed by coherent polarizations. Impulsive excitation of a coherent superposition of heavy- (HH) and light- hole (LH) states leads to pronounced beating phenomena, which were first found for excitons in quantum wells¹ and also recently in the free-carrier continuum of bulk gallium arsenide (GaAs).² At the absorption edge of GaAs, femtosecond pump-probe experiments are determined by both excitonic and free- carrier contributions. A direct experimental separation of the two components is still missing but mandatory for a complete interpretation of pump-probe data.

© 1998 Optical Society of America