Coherent and incoherent contributions to secondary emission

The coherent and incoherent contributions to the secondary emission of quan tum well excitons are calculated microscopically including the combined inf luence of phonons, photons and structural disorder. Increasing disorder lea ds to an overall larger signal with shorter rise time. After its initial in crease the coherence degree of the secondary emission gradually decays, and even when the initial signal is highly coherent, incoherent components dom inate at later times. Since phonon and disorder scattering are closely inte rrelated, the full secondary emission does not separate into additive contr ibutions from each of the mechanisms.