Abstract

The energy and momentum relaxation of optically excited free electron-hole pairs occurs via carrier-carrier scattering within a few hundred femtoseconds /1/. In contrast, little is known about the fast (momentum) relaxation processes of the excitonic groundstate. This lack of knowledge is partly due to the polariton character of excitons in a bulk semiconductor which impedes optical dephasing experiments in the time as well as in the frequency domain. A further problem especially for nonlinear experiments is the high absorption coefficient (10⁵ cm⁻¹) at the excitonic resonance leading to reabsorption of the nonlinear signal and necessitating a high excitation level, at which exciton-exciton interaction renders the interpretation of the experimental data /2/.

© 1986 Optical Society of America