Quantum trajectory studies of many-atom and finite transit-time effects in a cavity QED microlaser or micromaser

Studies of microlasers and micromasers generally assume that at most one atom is present in the resonator and transit times are much shorter than cavity lifetimes. We use quantum trajectory simulations to investigate the behavior of a microlaser/micromaser in which multiple atoms may be present and atom transit times can be comparable to the cavity decay time. Many-atom events are shown to destroy trap state resonances even for a mean intracavity atom number as small as 0.1. Away from trap states, results for mean photon number agree with a single-atom, weak-decay theory. However the variance of the photon number distribution increases relative to micromaser theory by an amount proportional to the product of the interaction time and cavity decay rate. This excess variance is interpreted as resulting from cavity decay during the atomic transit time.