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1996
Journal Article
Titel
Dephasing and selection rules of interband and intraband polarisations in superlattices
Alternative
Phasenentmischung und Auswahlregeln von Interband- und Intrabandpolarisationen in Übergittern
Abstract
We study the coherent dynamics of interband and intraband polarizations of Bloch oscillations in a GaAs/ Al(0.7)Ga(0,3)As semiconductor superlattice. Time-resolved measurements of both polarizations are simultaneously performed by combination of four-wave mixing and an electro-optic detection scheme in one experimental setup. This combination allows us to gain a much more comprehensive picture of the dynamics of a multi-level system. Distinctive differences in the oscillation frequencies and the dephasing of both polarizations are found. They arise from the fact that excitonic quantum beats are observed in four-wave mixing, whereas a quantum interference of electrons in continuum states is detected in the electro-optic signal. As a consequence, the polarizations are governed by different selection rules that explain the pronounced differences in the oscillation frequencies found for specific experimental conditions.
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