Infinite order excitonic Bloch equations for asymmetric nanostructures

We present a new exciton-based formalism for calculating the coherent response of asymmetric semiconductor multiple quantum well structures to ultra-short optical pulses valid to infinite order in the optical field and including the self-generated intraband fields. We use these equations to calculate and explain the oscillations with time delay of peaks in the spectrally-resolved degenerate four wave mixing signals from biased semiconductor superlattices, obtaining good agreement with experiment