Measured and calculated results are presented for the emission properties of a new class of emitters operating in the cavity quantum electmdynamics regime.The structures are based on high-finesse GaAs/AIAs micropillar cavities,each with an active medium consisting of a layer of InGaAs quantum dots (QDs) and the distinguishing feature of having a substantial fraction of spontaneous emission channeled into one cavity mode (high p-factor).This paper demonstrates that the usual criterion for lasing with a conventional (low β-factor) cavity,that is,a sharp non-linearity in the input-output curve accompanied by noticeable linewidth narrowing,has to be reinforced by the equal-time second-order photon autocorrelation function to confirm lasing.The paper also shows that the equal-time second-order photon autocorrelation function is useful for recognizing superradiance,a manifestation of the correlations possible in high-β microcavities operating with QDs.In terms of consolidating the collected data and identifying the physics underlying laser action,both theory and experiment suggest a sole dependence on intracavity photon number.Evidence for this assertion comes from all our measured and calculated data on emission coherence and fluctuation,for devices ranging from light-emitting diodes (LEDs) and cavity-enhanced LEDs to lasers,lying on the same two curves:one for linewidth narrowing versus intracavity photon number and the other for g(2)(0) versus intracavity photon number.