Impulsive excitation of cyclotron oscillations in a two-dimensional electron gas

We report on the impulsive excitation and control of intersubband and hybrid intersubband-cyclotron modes in a two-dimensional electron gas by ultrafast optical pulses. Pump-probe experiments were performed in the reflection geometry on a modulation-doped GaAs/AlxGa1−xAs quantum well at 7 K. Using a pulse shaper to produce multiple excitation pulses, we demonstrate coherent control of charge-density intersubband modes. When a tilted magnetic field is applied, we observe oscillations due to hybrid intersubband-cyclotron modes. The features observed in the pump-probe experiments are consistent in frequency and selection rules with spontaneous Raman scattering data obtained from the same sample.