Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: Semiconductor Laser II
HL 9.10: Vortrag
Montag, 26. März 2007, 17:00–17:15, H13
coherence properties of high-β semiconductor micropillar lasers — •Serkan Ates1, Sven Ulrich1, Stephan Reitzenstein2, Andreas Löffler2, Alfred Forchel2, and Peter Michler1 — 1Institut für Strahlenphysik, Universität Stuttgart, Allmandring 3, 70569 Stuttgart, Germany — 2Technische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
We will present our latest results of low temperature (T = 4 K) micro-photoluminescence (µ-PL), first-order field correlation g(1)(τ), and second-order field correlation g(2)(τ) measurements on high-β (≤ 0.12) semiconductor micropillar lasers with (InGa)As/GaAs quantum dots (QDs) as a gain material. A first identification of an onset of lasing was observed from µ-PL measurements which yield a smooth transition from spontaneous into stimulated emission in the input-output intensity characteristics. Based on these results, power-dependent g(1)(τ) measurements have been performed by Michelson interferometry to investigate the coherence properties of the emission throughout the transition regime. While the visibility of the emission’s self interference yield a Gaussian behavior below the smooth lasing onset with a coherence time of τc ≈ 30 ps, we observed a gradual change to a Lorentzian profile around the transition region. With increasing excitation, our measurements reveal a strong increase in τc (x10) of the emission which therefore reflects the change of emission characteristics from thermal to (mainly) stimulated (coherent) light. This observation was approved by g(2)(τ) correlation measurements which showed a strong reduction of intensity fluctuations above the transition regime.