Investigation of the nonresonant dot-cavity coupling in two-dimensional photonic crystal nanocavities

We study the optical emission from single semiconductor quantum dots coupled to the optical modes of photonic crystal nanocavities. For dots that are both spectrally and spatially coupled, autocorrelation measurements reveal efficient single photon generation, with a drastically reduced lifetime due to the Purcell effect. However, the multiphoton emission probability is enhanced compared to the same quantum dot (QD) transition when it is detuned from the cavity mode by controlled N2 deposition. This indicates the presence of an emission background that is shown to be related to the dot by using photon cross-correlation spectroscopy. Photon temporal correlations persist even for large spectral detunings beyond Δλ∼-10 nm, excluding the intrinsic QD continuum and phonon mediated processes as being responsible for the cavity mode emission background. We propose a mechanism based on photon induced shake up processes in the charged quantum dots, enhanced by the optical cavity.