We investigate theoretically the photon statistics in a coupled cavity system mediated by a two-level atom. The system consists of a linear cavity weakly driven by a continuous laser, and a nonlinear cavity containing an atom inside. We find that there exists a photon blockade in the linear cavity for both parameter regimes where the coupling strength between the atom and the nonlinear cavity is greater (or less) than the dissipation rate of the linear cavity. We also extend our model by pumping the two cavities simultaneously and find that the conventional photon blockade is apparent in the linear cavity, whereas the unconventional photon blockade appears in the nonlinear cavity. These results show that our work has potential applications for a single photon source in a weakly nonlinear system.
Quantized quasinormal-mode description of nonlinear cavity-QED effects from coupled resonators with a Fano-like resonance