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Femtosecond degenerate four‐wave mixing study of exciton coherence in wide‐gap II–VI quantum wells
Author(s) -
Häpl T.,
Nickolaus H.,
Henneberger F.,
Schülzgen A.
Publication year - 1996
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221940121
Subject(s) - biexciton , dephasing , exciton , femtosecond , degenerate energy levels , coherence (philosophical gambling strategy) , excitation , four wave mixing , physics , atomic physics , condensed matter physics , photon , molecular physics , chemistry , optics , nonlinear optics , quantum mechanics , laser
This paper studies coherent excitons in the presence of alloy disorder by femtosecond degenerate four‐wave mixing on ternary (ZnCd)Se/ZnSe quantum wells. The use of very low excitation densities enables to uncover an impurity‐mediated exciton dephasing time of (16 ± 2) ps and a related homogeneous exciton width of only 80 μeV. At higher densities, the coherence loss speeds up dramatically due to exciton‐exciton interaction. Separating the contributions from inhomogeneous (photon echo) and homogeneous broadening to the spectrally resolved decay transients allows to deduce the energy dependence of the dephasing time across the disorder broadened exciton ensemble. Further, pronounced biexciton resonances are observed in the signal spectrum which exhibit characteristic polarization properties. For cross‐polarized pulses, the biexciton signal shows a striking stimulation when the excitation density is increased.