Continuum contribution to excitonic four-wave mixing due to interaction-induced nonlinearities: A numerical study

Karim El Sayed, Dan Birkedal, Lyssenko Vadim, Jørn Märcher Hvam

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    Abstract

    We present a theoretical investigation of ultrafast transient four-wave mixing (FWM) of GaAs quantum wells for coherent excitation of excitons and a large number of continuum states. It is shown that in this case the line shape of the FWM signal is drastically altered due to an interaction-induced coupling of the exciton to all the excited continuum states. The signal is dominantly emitted at the spectral position of the exciton and decays, as a function of delay, on a time scale set by the duration of the laser pulse rather than by the intrinsic dephasing time. Nevertheless, the spectral width of the exciton line in the FWM spectrum and in the decay of the time-resolved FWM signal in real time are governed by the intrinsic excitonic dephasing rate. It is shown that for pulse durations of similar to 100 fs (for GaAs quantum wells) this behavior can be explained as the influence of the Coulomb exchange interaction, while for even shorter pulses this behavior is dominantly caused by nonlinear polarization decay.
    Original languageEnglish
    JournalPhysical Review B
    Volume55
    Issue number4
    Pages (from-to)2456-2465
    ISSN2469-9950
    DOIs
    Publication statusPublished - 1997

    Bibliographical note

    Copyright (1997) American Physical Society.

    Keywords

    • STATES
    • EXCITATION
    • GAAS
    • EXCITED SEMICONDUCTORS
    • WELLS
    • COULOMB QUANTUM KINETICS
    • 4-WAVE-MIXING SIGNALS
    • COHERENT DYNAMICS

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