Anharmonicity of Bloch oscillations in GaAs/AlAs superlattices in the case of inhomogeneously broadened excitonic states in a weak electric field

The variation of the spectral -shape of the four-wave mixing signal in GaAs/AlGaAs superlattices was studied experimentally and theoretically. It was shown that in an external electric field, leading to anticrossing of the levels of heavy and light excitons, sawtooth oscillations, of the energy position of the levels are observed. These oscillations are due to the inhomogencous broadening of the states participating in the Bloch oscillations.