Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 37: Quantum Dots and Wires: Optical Properties III

HL 37.11: Talk

Wednesday, March 24, 2010, 12:15–12:30, H15

Magnetic field controlled interaction strength of a strongly coupled quantum dot-micropillar system — •Steffen Münch, Stephan Reitzenstein, Philipp Franeck, Andreas Löffler, Sven Höfling, Lukas Worschech, and Alfred Forchel — Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

So far most experimental studies of strong coupling in QD-microcavity systems have relied on temperature tuning or electro-optical resonance tuning based on the quantum confined Stark effect. In this work we demonstrate that an external magnetic field provides a further degree of freedom to fully explore the potential of coherently coupled QD-microcavity system. We investigated magneto-optical resonance tuning of a laterally extended In_0.3Ga_0.7As QD embedded in the active layer of a micropillar cavity with a Q-Factor of 11000 which corresponds to a cavity mode linewidth of γ_C=120 µeV. Strong coupling with a QD exciton was observed at zero magnetic field exhibiting a Vacuum Rabi splitting (VRS) of 105 µeV. Magnetic field dependent studies show that the VRS and the associated coupling strength g decrease when magnetic confinement becomes significant above 3 T. This effect is explained in terms of a magnetic field dependent oscillator strength of the extended QDs. In this sense the magnetic field not only acts as a tuning parameter but also opens a way of in situ modifying the coupling strength of the interacting system. In a further approach we demonstrated spin-selective strong coupling by tuning Zeeman-split exciton lines sequentially through the cavity resonance.