Abstract

We present the first comparative study of the interband and intraband dynamics of coherent Bloch oscillations in the Wannier-Stark regime of GaAs/Al_xGa_1-xAs superlattices. Transmittive electro-optic sampling (TEOS) and degenerate four-wave mixing (FWM) experiments, which are sensitive towards the electronic intraband and excitonic interband dynamics, respectively, are performed simultaneously. Frequency differences in both experiments are observed with a pronounced dependence on the electric field. This effect shows that the Bloch oscillations observed are mainly performed by excitonic states in FWM and by continuum states in TEOS. The observation of non-excitonic Bloch oscillations is of prime importance for electrically driven Bloch oscillations and for the observation of Bloch oscillations at room temperature.

© 1995 Optical Society of America