Characterization of strong light-matter coupling in semiconductor   quantum-dot microcavities via photon-statistics spectroscopy
  It is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states. Using a microscopic theory, the second-rung resonance is analyzed and optimum excitation conditions are determined. The computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second-rung emission. 
L. Schneebeli, M. Kira, S.W. Koch