Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 18: Lasers and LEDs I

HL 18.5: Vortrag

Montag, 11. März 2013, 16:00–16:15, H16

Harmonic emission intensity modulation of a microlaser using picosecond acoustics — •Thomas Czerniuk¹, Christian Brüggemann¹, Andrey V. Akimov^2,3, Christian Schneider⁴, Sven Höfling⁴, Alfred Forchel⁴, Dimitri R. Yakovlev^1,2, and Manfred Bayer¹ — ¹Experimentelle Physik 2, TU Dortmund, 44221 Dortmund, DE — ²A. F. Ioffe Physical Technical Institute, 194021 St Petersburg, RU — ³School of Physics and Astronomy, University of Nottingham, NG7 2RD, UK — ⁴Technische Physik, Universität Würzburg, 97074 Würzburg, DE

We demonstrate a harmonic ∼10 GHz modulation of the microcavity laser emission intensity using picosecond strain pulses. The gain medium of the microlaser is an 11 meV broad inhomogenious InGaAs quantum dot ensemble. These QD’s are placed inside a resonant optical AlAs/GaAs Bragg reflector microcavity with a linewidth of 1.2 meV. This results in a inefficient coupling for a large fraction of the quantum dot ensemble to the laser mode. An optically excited broadband strain pulse propagates through the cavity and, once hitting the QD’s, shifts their transition energies by ∼10 meV within picoseconds. This couples more QD’s into the laser mode, thereby increasing the emission intensity. Due to the acoustic mismatch of AlAs and GaAs, the Bragg reflectors also work for phonons, increasing the lifetime of 16.6 GHz phonons inside the cavity. The effect is maximal, if the laser is pumped slightly above the lasing threshold, where we observe GHz modulations with a relative amplitude of 1.5 for more than 300 ps, much longer than the duration of the strain pulse.