title: Coherent nonlinear optical response of single quantum dots studied by ultrafast near-field spectroscopy.
abstract: The nonlinear response of single GaAs quantum dots is studied in femtosecond near-field pump-probe experiments. At negative time delays, transient reflectivity spectra show pronounced oscillatory structure around the quantum dot exciton line, providing the first evidence for a perturbed free induction decay of the excitonic polarization. Phase-disturbing Coulomb interactions between the excitonic polarization and continuum excitations dominate the optical nonlinearity on ultrafast time scales. A theoretical analysis based on the semiconductor Bloch equations accounts for this behavior.
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Guenther
authors.forename: Christoph
authors.initials: C
authors.lastname: Lienau
authors.forename: Thomas
authors.initials: T
authors.lastname: Elsaesser
authors.forename: Markus
authors.initials: M
authors.lastname: Glanemann
authors.forename: Vollrath Martin
authors.initials: VM
authors.lastname: Axt
authors.forename: Tilmann
authors.initials: T
authors.lastname: Kuhn
authors.forename: Soheyla
authors.initials: S
authors.lastname: Eshlaghi
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Wieck