PHOTON STATISTICS OF A CAVITY-QED LASER - A COMMENT ON THE LASER-PHASE-TRANSITION ANALOGY

We develop a birth-death model for a cavity QED laser and analyze the dependence of the lasing threshold on the fraction, , of spontaneous emission directed into the laser mode. We define threshold in terms of the Fano factor for the intracavity phonon number. We emphasize the role of as a parameter characterizing the system size and show that the concept of laser threshold is well-defined in the thermodynamic limit, -1. An ideal cavity-QED laser operates far outside this limit and therefore, in contrast to a conventional laser, is not a threshold device. We present numerical results showing how this difference affects the noise properties of the device. © 1994 The American Physical Society.