INTERNAL FIELD-DYNAMICS OF COHERENT BLOCH OSCILLATIONS IN SUPERLATTICES

The dynamics of coherent wavepacket oscillations in GaAs/AlxGa1-xAs su perlattices are investigated by transmittive electro-optic sampling (T EOS) with femtosecond time resolution. The internal polarization dynam ics of coherently superposed Wannier-Stark states in an externally bia sed superlattice, denoted as Bloch oscillations, can be monitored with high sensitivity in TEOS experiments. The amplitude, dephasing, and f requency of Bloch oscillations are studied as a function of applied el ectric field. The increasing localization of Wannier-Stark states at h igher fields results in a decreasing Bloch oscillation amplitude.