Direct observation of correlations between individual photon emission events of a microcavity laser


Lasers are recognized for coherent light emission, the onset of which is reflected in a change in the photon statistics1. For many years, attempts have been made to directly measure correlations in the individual photon emission events of semiconductor lasers2,3. Previously, the temporal decay of these correlations below or at the lasing threshold was considerably faster than could be measured with the time resolution provided by the Hanbury Brown/Twiss measurement set-up4 used. Here we demonstrate a measurement technique using a streak camera that overcomes this limitation and provides a record of the arrival times of individual photons. This allows us to investigate the dynamical evolution of correlations between the individual photon emission events. We apply our studies to micropillar lasers5 with semiconductor quantum dots2,3,6,7,8 as the active material, operating in the regime of cavity quantum electrodynamics9. For laser resonators with a low cavity quality factor, Q, a smooth transition from photon bunching to uncorrelated emission with increasing pumping is observed; for high-Q resonators, we see a non-monotonic dependence around the threshold where quantum light emission can occur. We identify regimes of dynamical anti-bunching of photons in agreement with the predictions of a microscopic theory that includes semiconductor-specific effects.

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Figure 1: Time-resolved photon counting statistics.
Figure 2: Measured second-order photon correlation function at zero delay time (top) and output intensity versus input pump power, P exc (bottom), for three different microcavity lasers.
Figure 3: Measured temporal evolution of the second-order correlation function for selected pump powers, Pexc.
Figure 4: Calculated zero-delay correlation functions, input–output curves and temporal dynamics of g(2)(τ).
Figure 5: Measured third-order correlation function g (3) (0).


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We would like to thank P. Gartner and I. Akimov for discussions and technical support. Funding from the Deutsche Forschungsgemeinschaft through the research group ‘Quantum optics in semiconductor nanostructures’ and a grant for CPU time at the Forschungszentrum Jülich (Germany) is gratefully acknowledged.

Author Contributions Experiments were performed in Dortmund by M.A., T.B. and M.B., with the participation of C. Kistner. Calculations were done in Bremen by J.W., C.G. and F.J. The III-V samples were grown in Würzburg by C. Kistner, S.R., C.S., S.H. and A.F. The II-VI sample was prepared in Bremen by C. Kruse, J.K. and D.H.

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Correspondence to F. Jahnke or M. Bayer.

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Wiersig, J., Gies, C., Jahnke, F. et al. Direct observation of correlations between individual photon emission events of a microcavity laser. Nature 460, 245–249 (2009).

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