Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 12: Quantenpunkte und -dr
ähte: Optische Eigenschaften II
HL 12.3: Vortrag
Freitag, 4. März 2005, 15:30–15:45, TU P-N201
Heterodyne Four-Wave Mixing on Single Excitonic States — •Brian Patton1, Wolfgang Langbein2, and Ulrike Woggon1 — 1Experimentelle Physik IIb, Universität Dortmund, Otto-Hahn-Straße 4, 44221 Dortmund — 2School of Physics and Astronomy, Cardiff University, Cardiff, Wales, UK
Coherent optical spectroscopy on excitonic states allows insights into the underlying physics and opens up the possibility of manipulation of individual quantum states. Non-degenerate four-wave mixing and pump-probe spectroscopy are currently the main techniques. Instead, we use a novel heterodyne four-wave mixing technique which, by spectral interference with a reference signal, allows us to recover both the amplitude and phase of the third-order nonlinear polarisation of the single state. High-NA imaging of the sample allows the recovery of the resonant transient nonlinearity of single localized excitons. Furthermore, the knowledge of the phase of our signal allows subsequent analysis in both time and frequency domains. We have also narrowed the excitation to a single state and used a strong pump pulse to allow us to coherently drive the polarisation of the individual exciton by a desired angle in the Bloch sphere. We analyse the observed Rabi oscillations in the exciton polarisation with regard to the polarisation decay of the transition and we were able to rule out excitation induced dephasing as the source for observed deviations in the behaviour of the oscillations from the ideal 2-level system.