Absorption recovery in strongly saturated quantum-well electroabsorption modulators

We observe experimentally that a quantum-well electroabsorption modulator, when strongly saturated by a highly energetic optical pulse, may exhibit an absorption recovery time much longer than for excitation with a low-energy pulse. Using a comprehensive drift-diffusion type model, we are able to explain this effect theoretically. The prolongation of the absorption recovery is induced by carrier distribution effects, not by field-induced changes in the dynamical transport parameters such as the time carriers take to escape from the wells.