A microscopic theory for optical gain in semiconductor quantum dots

We study the optical properties of semiconductor quantum dots by means of a quantum-kinetic theory. The excitation-induced dephasing and the corresponding line-shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined and used in conjunction with the usual ingredients of a gain calculation like Coulomb enhancement and State filling to set up a microscopic calculation of the quantum dot gain. We find that for very high carrier densities in QD systems the maximum of the optical gain can decrease with increasing carrier density due to a delicate balancing between state filling and dephasing.