Terahertz Linear and Nonlinear Dynamics in Confined Magnetoexcitons

We have probed the linear and nonlinear terahertz (THz) properties of magnetoexcitons in GaAs/AlGaAs quantum wells. By monitoring photoluminescence from the quantum wells that were simultaneously driven by THz fields, we have directly observed internal transitions of excitons. In the nonlinear, high-THz-excitation regime, we observed mixing of optical and THz radiation, which resulted in THz optical sidebands. By monitoring the sidebands, we observed oneand two-THzphoton nonlinear internal transitions in excitons. These results provide new and accurate information on the energy structure and internal dynamics of excitons.