How fast is excitonic electroabsorption?

Many semiconductor light modulators rely on changes in excitonic absorption induced by electric fields. We study their temporal response in the framework of a one-dimensional model, for which we solve exactly the timedependent Schrödinger equation. For a homogeneously broadened system, the electroabsorption response time is found to be simply the inverse of the (field-induced) exciton linewidth, which can be as short as 50 fsec.