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physica status solidi (b)

Femtosecond Coherent Spectroscopy of GaAs Quantum Wells

Dai‐Sik Kim, Jagdeep Shah, Wilfried Schäfer, Stefan Schmitt-Rink

Published Sep 1, 1992• 10 citations
Publisher

Abstract

Abstract Recent results on femtosecond time‐integrated and time‐resolved four‐wave‐mixing experiments in intrinsic and modulation‐doped GaAs quantum wells are reported. A variety of new phenomena ranging from giant excitonic resonance for intrinsic samples, Fermi liquid behavior in modulation‐doped samples, and interesting temporal evolutions provide new insights into the physical process responsible for the coherent signals.

DOI
10.1002/pssb.2221730102

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Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum beats are observed up to excess energies of 75 meV above the exciton resonances. The experimental data clearly demonstrate the coherence of continuum states in the valence band. Changes of the beat frequency with the excitation energy are due to the dispersion of the valence bands.