Cavity QED beyond the Jaynes–Cummings model

As atom-cavity systems are becoming more sophisticated, the limitations of the Jaynes–Cummings model are becoming more apparent. In this paper, we therefore take a more dynamical approach to the modelling of atom-cavity systems and do not reduce the electromagnetic field inside the resonator to a single mode. Our approach shows that the decay rate Γcav of an emitter inside a subwavelength cavity with metallic mirrors can be much larger than its free space decay rate Γfree due to constructive interference effects of the emitted light. In general, however, we find that Γcav =Γfree to a very good approximation which might explain why atom-cavity experiments with planar mirrors have not been able to operate in the so-called strong coupling regime.