Transition to a multiphoton excitonic response in GaAs

Peter Kner

R. Cingolani, Maria Antonietta Lepore, Raffaele Tommasi +7 more

We have investigated the polarization-dependent two-photon absorption in GaAs/AlGaAs quantum wires. The anisotropic selection rules of the multiphoton absorption process are exploited to study the one-dimensional 2p exciton states and the transitions between quantum wire subbands of different quantum numbers (\ensuremath{\Delta}${\mathit{n}}_{\mathit{y}}$\ensuremath{\ne}0 selection rule). The deviations from the selection rules derived for the strict one-dimensional case are discussed, and depend on the actual quasi-one-dimensional character of the excitonic wave functions.

Lothar Schultheis, J. Kühl, A. Honold +1 more

Daniel Webber, Brian L. Wilmer, Xiao Liu +4 more

Transient four-wave mixing studies of bulk GaAs under conditions of broad bandwidth excitation of primarily interband transitions have enabled four-particle correlations tied to degenerate (exciton-exciton) and nondegenerate (exciton-carrier) interactions to be studied. Real two-dimensional Fourier-transform spectroscopy (2DFTS) spectra reveal a complex response at the heavy-hole exciton emission energy that varies with the absorption energy, ranging from dispersive on the diagonal through absorptive for low-energy interband transitions to dispersive with the opposite sign for interband transitions high above band gap. Simulations using a multilevel model augmented by many-body effects provide excellent agreement with the 2DFTS experiments and indicate that excitation-induced dephasing (EID) and excitation-induced shift (EIS) affect degenerate and nondegenerate interactions equivalently, with stronger exciton-carrier coupling relative to exciton-exciton coupling by approximately an order of magnitude. These simulations also indicate that EID effects are three times stronger than EIS in contributing to the coherent response of the semiconductor.

K. Bott, O. Heller, D. Bennhardt +7 more

The degenerate-four-wave-mixing response of excitons in GaAs quantum wells is modeled using the optical Bloch equations including exciton-exciton interactions. The results display a strong dependence on the polarization of the excitation pulses. The model predicts intensity and polarization dependences of the time-integrated signal and characteristic temporal features of the time-resolved and time-integrated response in excellent agreement with observations.

T. Kühn, Eberhard Binder, Fausto Rossi +6 more