We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the 1s exciton emission, which we attribute to the terahertz-induced 1s-to-2p excitation. Simultaneously, a pronounced enhancement of the 2s exciton emission is observed, despite the 1s-to-2s transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2s and 2p states, yielding an effective terahertz transition between the 1s and 2s populations.

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Time-resolved terahertz quenching studies of the magnetoexcitonic photoluminescence from GaAs/AlGaAs quantum wells are performed. A microscopic theory is developed to analyze the experiments. Detailed experiment-theory comparisons reveal a remarkable magnetic-field controllability of the Coulomb and terahertz interactions in the excitonic system.

Terahertz‐induced intra‐exciton transitions are studied in semiconductor quantum‐well systems under the influence of a constant magnetic field. A systematic description is developed to include carrier–carrier interactions, terahertz transitions, and magnetic‐field effects to the exciton‐correlation dynamics. When a magnetic field is present, the exciton states and energies are changed directly and parametrically via the center‐of‐mass momentum of excitons. The numerical results show that both effects influence the terahertz spectroscopy. Especially, the transition between 1s‐ and 2p‐exciton states is shown to depend strongly on both magnetic field and center‐of‐mass momentum. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper discusses recent studies involving time‐resolved optical and terahertz (THz) fields in the linear and nonlinear regime. An overview of the microscopic modeling scheme is presented and applied to analyze a variety of experimental results. The examples include coherent excitons in weak and strong THz fields, Rabi splitting and ionization of intra‐excitonic transitions, THz studies in semiconductor microcavities, and the THz manipulation of excitonic transitions.