Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 4: Ultrakurzzeitph
änomene

HL 4.2: Vortrag

Montag, 8. März 2004, 10:30–10:45, H13

Dephasing of excitonic and biexcitonic polarization: Intensity and temperature dependence — •Lars Wischmeier, Hans Georg Breunig, Tobias Voss, Ilja Rückmann, and Jürgen Gutowski — Institut für Festkörperphysik, Universität Bremen, P.O. Box 330440, D-28334 Bremen

The decay of coherent excitonic and biexcitonic polarization was investigated in a high quality 10 nm ZnSe/ZnS_0,07Se single quantum well as a function of intensity, temperature (4 − 70 K), and polarization of the 110 fs excitation pulses. The spectral position of the pulses was tuned such that the resonances of the 1s heavy-hole exciton and the biexciton were exclusively excited. The dephasing rates were obtained by both four-wave-mixing (FWM) and pulse-transmission measurements. The experimental results were fitted with the temperature dependence of the homogeneous linewidth due to phonon scattering. From the temperature dependence of the decay of the FWM signal of the excitonic and biexcitonic polarizations the acoustic- and optical-phonon-scattering coefficients were determined.

Additionally the contrast ratio obtained from coherent-control measurements with two phase locked pulses was studied as a function of temperature and intensity.