/spl chi//sup (5)/-signatures in the optical Stark effect

Summary form only given. Recently a lot of interest has been focused on higher-order Coulomb correlations. It was shown, that even in the /spl chi//sup (3)/-limit higher-order excitonic correlations, i.e., bound and unbound two exciton states, influence the coherent optical response. While /spl chi//sup (3)/-contributions to the excitonic Stark effect are well understood, very little is known about the influence of /spl chi//sup (5)/-contributions. Here we investigate the dependence of coherent pump-induced excitonic absorption changes on the pump intensity and relate our results to fifth-order contributions. Pump-probe experiments are performed on high-quality InGaAs quantum wells dominated by a heavy-hole exciton resonance.