Dephasing of Excitons in ZnSe Quantum Wells Using Ultrashort Excitation Pulses

We report on the decoherence of excitons in ZnSe single quantum wells by intensity dependent four‐wave‐mixing (FWM) experiments using 30 fs pulses. The FWM traces at the 11h exciton transition reveal marked quantum beats and a fast decay at pulse overlap that is attributed to a destructive interference of the polarization wavepacket and to an effective diffraction of the exciton polarization at an electron‐hole‐pair density grating. Three‐pulse FWM experiments are performed to study the formation of excitons from this electron‐hole‐pair grating.