Validation of Lasing in Active Nanocavities

An unambiguous proof of lasing in an active nanocavity with ultrahigh spontaneous emission coupling factor (beta = 0.65) is presented. To distinguish the subtle lasing threshold features from possible material-related phenomena, such as saturable absorption in the gain medium, a series of active nanocavities with different values of beta have been designed to systematically approach the high-beta device. The demonstration of the lasing threshold is obtained through the observation of the transition from thermal to coherent light photon statistics that is well understood and identified in the beta << 1 lasing regime. The systematic investigation allows a more definitive validation of the onset of lasing in these active nanocavities.