Excitonic polarization dephasing under strong resonant pulsed excitation in GaAs quantum wells

Bipul Pal and A. S. Vengurlekar
Phys. Rev. B 66, 155337 – Published 31 October 2002
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Abstract

We study the coherent response of an optically dense exciton system in GaAs quantum wells (QWs). For this, we resonantly excite 1s heavy-hole excitons in the QWs at 8 K with subpicosecond laser pulses. The excitonic polarization is probed using time integrated (TI) degenerate four wave mixing (DFWM) measurements in self-diffraction geometry. The average power density (I1) of the leading laser pulse is systematically increased to large values, keeping that of the delayed pulse small and fixed. The dephasing rate of the excitonic coherent polarization (determined by the rate of decrease of the TI-DFWM signal with delay between the exciting pulses) attains saturation at large I1 after an initial rise at small I1. In comparison, the coherent polarization (as given by the DFWM signal at a fixed delay) increases initially with I1, reaches a peak and then decreases at large I1.

  • Received 4 April 2002

DOI:https://doi.org/10.1103/PhysRevB.66.155337

©2002 American Physical Society

Authors & Affiliations

Bipul Pal* and A. S. Vengurlekar

  • Tata Institute of Fundamental Research, Mumbai 400005, India

  • *Electronic address: bipulpal@tifr.res.in

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Vol. 66, Iss. 15 — 15 October 2002

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