Temperature dependence of the intraexcitonic AC Stark effect in semiconductor quantum wells

We have investigated the temperature-dependent, intraexcitonic AC Stark effect that manifests itself in a line splitting of the heavy-hole 1s exciton transition in a GaAs/AlGaAs multi quantum well when the 1s-2p intraexciton transition is driven by intense THz light. The observed wavelength-dependent splitting at Helium temperature can still be distinguished at elevated temperatures up to 200 K. Although the thermal energy exceeds the exciton binding energy by a factor of 1.7, thermal exciton ionization influences the coherent nonlinear effect only indirectly via thermal line broadening. With a threefold transmission change on ultrafast timescales in a region accessible to Peltier-cooling the scheme could be promising for optical modulators.