The ultrafast carrier dynamics of Ge/SiGe quantum wells on Si substrate are investigated by pump-probe spectroscopy. Pronounced nonequilibrium effects in the relaxation dynamics and transient gain are observed and analyzed using a microscopic many-body theory.

A microscopic theory for secondary emission of a semiconductor quantum well is presented where disorder and phonon scattering are treated consistently. Coherent and incoherent contributions to the secondary emission are computed for model systems with different degrees of disorder. The results show that the simultaneous influence of both scattering mechanisms is generally nonadditive, such that a full calculation is required to obtain reliable results. Only in strongly disorder dominated structures it is a reasonable approximation to model phonon scattering by a phenomenological decay time.

High-resolution amplitude and phase linear spectroscopy of high-quality bulk GaAs are reported. The detailed structure of the observed full complex transmission is consistently explained by polariton effects on the basis of microscopic calculations. The coupled equations for the excitonic polarization and the light field in the slab configuration are evaluated using appropriate boundary conditions for the electromagnetic field and the excitonic wave function without reference to additional boundary conditions for the macroscopic polarization.

The phonon scattering assisted luminescence of semiconductor quantum well excitons after short pulse excitation is investigated. The presented analysis is based on the low-density limit of a set of equations for quantum correlation functions for electrons, phonons, and photons. The dynamics of the correlation functions describes the optical excitation and the decay of the coherent exciton polarization as well as the generation of an incoherent exciton occupation and its luminescence decay. Numerical solutions of the equations of motion demonstrate strong competition effects of the exciton-phonon and the exciton-photon interaction on a picosecond time scale and lead to a nonmonotonous temperature dependence of the time-resolved spontaneous emission. The angle resolved emission resembles the generation and decay dynamics of the exciton density for different in-plane momenta.