Interplay of optical dephasing and pulse propagation in semiconductors

A comprehensive numerical study of the influence of electron-hole scattering on optical dephasing and related pulse propagation phenomena in semiconductor waveguide media is presented. The material equations incorporate a hierarchy of incoherent scattering mechanisms including inscattering and outscattering and higher-order polarization scattering processes into the optical polarization; these mechanisms are treated on the level of quantum Boltzmann equations. For optically excited semiconductor absorbers a dramatic increase of the dephasing time of the optical polarization is demonstrated theoretically for excitation conditions near the band edge, in comparison with excitation high into the continuum. These results are applied to model pulse propagation high above the band gap and at the exciton resonance, which display qualitatively different behavior. For the semiconductor amplifier it is shown that the inscattering mechanisms are important for an accurate description of linear gain spectra. Nonlinear pulse propagation is also studied for excitation at the peak gain of the optical amplifier.