Femtosecond coherent spectroscopy of etched quantum wires

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Abstract
We report measurements of the homogeneous linewidth of an excitonic resonance in a quantum wire. Transient time-integrated and time-resolved four-wave-mixing experiments are used to obtain the homogeneous linewidth by measuring the dephasing time. A biexponential decay is observed and attributed to the presence of free and localized excitons. The homogeneous linewidth for both species is measured as a function of temperature and excitation density. Quantum beats are observed due to interference between the m=1 and m=2 center-of-mass-quantized n=1 heavy-hole exciton states.