Based on a microscopic many-particle theory, we predict large optical gain in the probe and background-free four-wave mixing directions caused by excitonic instabilities in semiconductor quantum wells. For a single quantum well with radiative-decay limited dephasing in a typical pump-probe setup we discuss the microscopic driving mechanisms and polarization and frequency dependence of these instabilities.
@article{arxiv.0708.0442,
title = {Large optical gain from four-wave mixing instabilities in semiconductor quantum wells},
author = {S. Schumacher and N. H. Kwong and R. Binder},
journal= {arXiv preprint arXiv:0708.0442},
year = {2009}
}