Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Quantum Dots and Wires, Optical Properties IV: Spin

HL 55.5: Talk

Thursday, March 25, 2010, 15:00–15:15, H14

Creation of mode-locked spins by up to 80 ps pulses — •Steffen Varwig¹, Stefan Spatzek¹, Alexander Schwan¹, Irina A. Yugova², Mikhail M. Glazov³, Dmitri R. Yakovlev^{1, 3}, Dirk Reuter⁴, Andreas D. Wieck⁴, and Manfred Bayer¹ — ¹Experimentelle Physik II, TU Dortmund, D-44221 Dortmund, Germany — ²Institute of Physics, St. Petersburg State University, 198504 St. Petersburg, Russia — ³A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia — ⁴Angewandte Festkörperphysik, Ruhr- Universität Bochum, D-44780 Bochum, Germany

Precessing electron spins in an ensemble of singly charged quantum dots are of high interest for quantum information processing. To overcome the problem of fast spin dephasing due to inhomogenities within a quantum dot ensemble, it was shown that it is possible to synchronize the precession modes of the electron spins to the repetition rate of the exciting laser [1].

In previous measurements mode-locking was studied by a pump-probe technique with a laser repetition rate of 13.2 ns and a pulse duration of 2 ps. The spectral pulse width was about 1.5 nm. With a smaller bandwidth less quantum dots are excited, thus presumably increasing the spin dephasing time. However, the excitation time has to be short in comparison to a precession period. Hence, we investigated the influence of pulses with durations up to 80 ps and corresponding bandwidths of 0.6 nm on the possibility of mode-locking in spin ensembles.

[1] A. Greilich et al., Science 313, 341 (2006).