Cavity Emission and Photon Statistics in Exciton-Cavity Coupled Systems


Takehiko Tawara, Hidehiko Kamada, and Stephen Hughes*
Optical Science Research Laboratory, *Queen’s University

 Interaction between single exciton and single cavity mode are fundamentally interesting and useful in the context of single-photon source for quantum information processing. A curious feature in recent studies using semiconductor photonic-crystal (PhC) is much brighter cavity emission under large detuning than theoretically expected from standard emission formulas [1]. Here, we undertake an experimental study to identify the cavity mode emission at non-zero detuning and its influence on single photon statistics [2].
 We use PhC cavities which consist of a GaAs membrane containing a single InAs dot layer. The left panel of Fig. 1 is image of PL intensity mapping with cavity mode detuning at 4 K. The GaAs barrier was excited by Ar-ion laser (2.54 eV) in this measurement. We found that this system show the bright cavity emission even under fairly-large detunings. The integrated PL intensity when the cavity mode and the exciton are resonant (zero detuning), increases by a factor of about 9 compared with the off resonant case.
 To explore the influence of the cavity emission on the photon statistics, we measured the second-order autocorrelation function of the photon intensity. When off-resonant cavity mode, anti-bunching was not observed where gC((2))(0) 〜1. This absence of the non-classical correlation on the cavity mode is attributed to independently emitted photons from the background such as deep defect level in the GaAs layer. The off-resonant exciton exhibited partial anti-bunching with gX((2)) (0)=0.57, indicating that quantum mechanical coupling prevails. Interestingly, at zero detuning the autocorrelation of the overlapping exciton and cavity modes shows a better anti-bunching with gC((2))+X (0)=0.35. As the exciton-cavity coupling is stronger, the relative weight of the deep states recombination contribution decrease, thereby the anti-bunching behavior is recovered to a better g ((2))(0), indicating that the photon statistics becomes more non-classical. These measurements are well explained using a medium-dependent master equation model.
 This work was partially supported by Strategic Information and Communications R&D Promotion Programme (SCOPE) of Japan.

[1] For example, K. Hennessy et al., Nature 445 (2007) 896.
[2] T. Tawara et al., Opt. Express 17 (2009) 6643.

Fig. 1. PL intensity mapping with cavity mode detuning and 2nd order autocorrelation functions.

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