Resonant Terahertz Optical Sideband Generation from Confined Magnetoexcitons

Abstract

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 ${\ensuremath{\omega}}_{\mathrm{NIR}}\ifmmode\pm\else\textpm\fi{}2n{\ensuremath{\omega}}_{\mathrm{THz}}$, where ${\ensuremath{\omega}}_{\mathrm{NIR}}$ is the interband exciton-creation frequency, ${\ensuremath{\omega}}_{\mathrm{THz}}$ is the frequency of the driving field, and $n$ is an integer. The intensity of the sidebands exhibits pronounced enhancement when ${\ensuremath{\omega}}_{\mathrm{THz}}$ coincides with transitions between magnetically tuned energy levels in the excitons, providing new and accurate information on the internal dynamics of excitons.