Journal article
Coherent Exciton and Biexciton Nonlinearities in Semiconductor Nanostructures: Effects of Disorder
The coherent response of excitons in semiconductor nanostructures measured in four-wave mixing (FWM) depends strongly on the inhomogenous broadening of the exciton transition. We investigate InAs/Al0.3Ga0.7As single quantum wells (SQW) and AlxGa1-xAs mixed crystals. Additional to the usual phase-space filling nonlinearity, excitation-induced dephasing (EID) and biexciton formation (BIF) are important.
EID leads to a strong dependence of the signal on the angle between the linear input polarizations. We find that EID persists in inhomogeneous systems, showing that the mutual density-dependent dephasing rate difference between two subsystems within the inhomogeneous distribution is strongly dependent on their energy difference.
BIF is strongly affecting the cross-linear polarized FWM response. The signal for positive delay is dominated by the transitions from the one-exciton state X to the two-exciton-states. Here, the third-order polarization at X-XX is not at the same resonance as the first-order polarization at 0-X. Consequently, the rephasing of the microscopic third-order polarization to the macroscopic FWM photon echo is blurred by the non-perfect correlation of X and XX energies, leading to a fast and non-exponential signal decay in delay time.
For inhomogenous broadenings larger than the biexciton binding energy, we find an enhanced biexciton binding energy, and a quenching of the oscillator strength of the unbound biexciton.
Language: | English |
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Publisher: | Trans Tech Publications Ltd |
Year: | 1999 |
Pages: | 73-78 |
ISSN: | 16629752 , 02555476 and 14226375 |
Types: | Journal article |
DOI: | 10.4028/www.scientific.net/MSF.297-298.73 |
ORCIDs: | Hvam, Jørn Märcher |