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HL: Fachverband Halbleiterphysik
HL 44: Poster Session I
HL 44.21: Poster
Tuesday, March 15, 2011, 18:00–21:00, P3
Giant dynamical Stark shift in germanium quantum wells — •Ronja Woscholski1, Niko Steffen Köster1, Kolja Kolata1, Christoph Lange1,3, Giovanni Isella2, Daniel Chrastina2, Hans von Känel2, and Sangam Chatterjee1 — 1Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany — 2Dipartimento di Fisica del Politecnico di Milano, Polo di Como, via Anzani 42, I-22100 Como, Italy — 3present address: University of Toronto, Department of Physics, 60 St. George St., Toronto ON, M5S 1A7, Canada
One of the goals in semiconductor research is to realize the necessary components for silicon photonics, like detectors, emitters, and modulators. Here, we show the potential of Ge/SiGe quantum well structures to work as optical modulators. We investigate the dynamical Stark effect by using polarization-resolved ultrafast pump and white-light probe spectroscopy. This method offers insight on both the modulation bandwidth and the switching speeds achievable in this material system. A strong blue shift of more than 150meV is found for a sample temperature of 10K, which exceeds the values typically for III-V materials. The experimental results are in good agreement with the dressed exciton model. We conclude that the ultrafast coherent dynamics are mainly governed by the direct transition; the indirect minima play only a minor role.