Resonant terahertz optical sideband generation from confined magnetoexcitons

We have probed the internal structure and nonlinear response of magnetoexcitons in GaAs/AlGaAs quantum wells by resonantly driving one-and two-photon internal transitions with intense terahertz electric fields. Strong near-band-gap emission lines, or optical sidebands, appear at frequencies omega(NIR) +/- 2n omega(THz), where omega(NIR) is the interband exciton-creation frequency, omega(THz) is the frequency of the driving field, and n is an integer. The intensity of the sidebands exhibits pronounced enhancement when omega(THz) coincides with transitions between magnetically tuned energy levels in the excitons, providing new and accurate information on the internal dynamics of excitons.