Emission from driven atoms in collective strong coupling with an optical cavity

We study self-sustained cavity emission from driven atoms in collective strong coupling. The cavity emission occurs over a wide range of atom-cavity and drive-laser detunings without any external input to the cavity mode. Second-order correlation measurements ${g}^{(2)}(\ensuremath{\tau})$ further reveal unanticipated phenomena in the observed cavity emission such as (1) damped oscillations at two frequencies and (2) significantly distinct ${g}^{(2)}(\ensuremath{\tau})$ for different polarization components. The intricate relation between cavity-emission intensity, drive-laser detuning, and atom-cavity detunings is explained. A possible mechanism for the damped oscillations with two frequency components in ${g}^{(2)}(\ensuremath{\tau})$ is suggested. Measurements show the existence of two separate polarization-decoupled mechanisms with distinct photon statistics, through which energy is transferred from the drive field to the cavity field. The statistical properties and mechanisms underlying cavity emission present valuable insights for extending nondestructive detection techniques to the regime of collective strong coupling.