  The two-color optical coherence absorption spectrum (QUIC-AB) of GaAs quantum
well in the presence of a charge current is investigated. We find that the
QUIC-AB depends strongly not only on the amplitude of the electron current but
also on the direction of the electron current. Thus, the amplitude and the
angular distribution of scattering current in the scatter process can be
detected directly in real time with the QUIC-AB. The phase shift of scattered
waves and the details of the scattering potential can also be determined.
