Abstract

Already in 1986 two groups observed a Stark shift of the fundamental exciton transition in semiconductors for pumping below the resonance [1,2]. However, to our knowledge, no observation for above-resonance excitation of free excitons has been reported so far. Interest in this arises from the theoretical point of view: While for a two-level system the sign of the Stark shift is expected to change when tuning the excitation energy across the resonance, a Hartree-Fock approach for free excitons [3,4] yielded a blue shift independent of the pump detuning δ.

© 1996 Optical Society of America