  We experimentally investigated the excitation power dependence of a strongly
coupled quantum dot (QD)-photonic crystal nanocavity system by
photoluminescence (PL) measurements. At a low-excitation power regime, we
observed vacuum Rabi doublet emission at QD-cavity resonance condition. With
increasing excitation power, in addition to the doublet, a third emission peak
appeared. This observed spectral change is unexpected from conventional atomic
cavity quantum electrodynamics. The observations can be attributed to featured
pumping processes in the semiconductor QD-cavity system.
