Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 20: Symposium: Single Photon Sources and Spectroscopy of Individual Quantum Systems
HL 20.5: Vortrag
Samstag, 5. März 2005, 12:45–13:15, TU P270
Voltage-Controlled Optics of a Single Quantum Dot — •Khaled Karrai1, Alexander Högele1, Stefan Seidl1, Martin Kroner1, Richard J. Warburton2, Brian D. Gerardot3, and Pierre M. Petroff3 — 1Center for NanoScience and Department für Physik, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München, Germany — 2School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom — 3Materials Department, University of California, Santa Barbara, California 93106, USA
We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. Using a newly developed high-resolution laser spectroscopy method we find that the transmission spectrum of the neutral exciton exhibits two narrow lines with about 2 micro-eV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. We show that choosing a gate voltage where the dot is occupied with an additional electron turns off the exchange interaction. In this regime, the negatively charged exciton has no dark states. Saturation spectroscopy demonstrates that the neutral and the negatively exciton behaves as a two-level system. Our experiments show that the remaining problem for preparing and manipulating excitonic quantum states in this system is possibly spectral fluctuation on a micro-eV energy scale.