Optical injection and coherent control of a ballistic charge current in GaAs/AlGaAs quantum wells

We report all-optical injection and coherent control of a ballistic charge current in GaAs/AlGaAs quantum wells. This current arises through quantum interference of one- and two-photon absorption of similar to100 fs pulses with parallel linear polarizations, and its magnitude can be controlled by adjusting the relative phase of the incident pulses. By monitoring differential transmission using a spatially resolved optical pump-probe technique, we observe evidence of carrier motion associated with this ballistic current. Results are consistent with a theoretical treatment specific to quantum wells, and are qualitatively similar to previous measurements in bulk GaAs. (C) 2003 American Institute of Physics.