COHERENT DYNAMICS OF EXCITONIC WAVE-PACKETS

We report on the coherent dynamics of excitonic wave packets observed in transient four-wave mixing experiments on strained InGaAs/GaAs quan tum-well structures. The excitonic noneigen-states are created by usin g laser pulses shorter than the electron round trip time within the ex citon orbital. A characteristic temporal modulation of the diffracted signal is observed, which resembles the coherent dynamics of an electr on wave packet in a hydrogen atom expected for the case of a simultane ous excitation of all bound and the lowest continuum states.