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HL: Fachverband Halbleiterphysik

HL 95: Quantum Dots and Wires: Optical Properties III (mainly Cavities and Ultrafast Response)

HL 95.5: Talk

Friday, March 30, 2012, 10:30–10:45, EW 201

Ultrafast switching of a semiconductor quantum dot exciton — •Christian Dicken^1,2, Christian Wolpert^1,2, Klas Lindfors^1,2, Harald Giessen^1,2, and Markus Lippitz² — ¹Max Planck Institute for Solid State Research, Ultrafast Nanooptics — ²University of Stuttgart, 4th Physics Institute

We report on ultrafast switching of the neutral exciton transition of a single GaAs quantum dot on the 50 ps timescale. In our experiment, an electron-hole plasma is created in the vicinity of the quantum dot by a strong 150 fs off-resonant laser pulse. As a consequence we observe in transient reflection a reduction of the transition dipole moment by typically 50 % and a redshift of the absorption line of up to 100 µ eV. Both effects follow the dynamics of the electron-hole plasma and are strongly power dependent. We discuss the control and enhancement of the switching by confining the electron-hole plasma spatially.