COHERENT DYNAMICS AND DEPHASING OF ONE-DIMENSIONAL MAGNETOEXCITONS INGAAS

We study the ultrashort dynamics and the dephasing processes of one-di mensional Lorentzian and Fano magnetoexcitons in GaAs, using temporall y and spectrally resolved four-wave mixing. The dephasing of the Loren tzian magnetoexcitons is determined by quasi-particle scattering, domi nated by exciton-exciton scattering at low temperatures. In contrast, the dephasing time of the Fano magnetoexcitons is intrinsically limite d by the Fano coupling to the continuum. Quantum interference is obser ved if Fano magnetoexcitons contribute to the four-wave mixing signal. This effect is absent in the case of purely Lorentzian dynamics. We s how that Lorentzian and Fano magnetoexciton resonances are coupled by Coulomb correlation and discuss the consequences of this coupling. (C) 1996 Optical Society of America.