  Luminescence intensity autocorrelation (LIA) is employed to investigate
coupling dynamics between (In,Ga)As QDs and a high-Q (~7000) resonator with
ultrafast time resolution (150 fs), below and above the lasing threshold at T =
5 K. For QDs resonant and non-resonant with the cavity we observe both a
six-fold enhancement and a 0.77 times reduction of the spontaneous emission
rate, respectively. In addition, LIA spectroscopy reveals the onset of coherent
coupling at the lasing threshold through qualitative changes in the dynamic
behavior and a tripling of the resonant QD emission rate.
