Monoatomic optical diode based on direction-dependent bistability in the Purcell regime

Until now, single-atom bistability has been widely discussed in strong coupling regime. Here we focus on the scattering property of single atom-cavity coupling system in the Purcell regime, in which optical bistability was not predicted due to adiabatic treatment. In our previous works, we have shown concisely that optical bistability exists in part of the Purcell regime due to the presence of giant single-atom saturation nonlinearity, and the properties of bistable regime rely on the incident direction of input light within asymmetric cavity. Such direction-dependent bistability and its potential application as an efficient optical diode are discussed elaborately in this work. After comprehensive analysis, the thresholds of parameters to discriminate bistable regime from non-bistable regime are presented in detail. The limitation of adiabatic treatment which was widely adopted in the Purcell regime is also surveyed, which shows that only when the selected parameters are far from the bistable regime can the evolution of the cavity field be treated adiabatically. Direction-dependent bistability make it feasible to construct such monoatomic optical diode with high transmission contrast.