We theoretically study the photon blockade (PB) effect in a double-cavity optomechanical system with the two-photon driving. By analytical calculations and numerical simulations, the physical mechanisms of conventional photon blockade (CPB) and unconventional photon blockade (UPB) are discussed in detail. And then we obtain the optimal parameter conditions for PB. In our work, there exist both the CPB induced by strong nonlinear interaction and the UPB caused by quantum interference. In particular, we find that CPB and UPB can occur simultaneously under the same parameters. In addition, we also prove that the appropriate values of nonreciprocal coupling and two-photon driving are favorable to the improvement of PB. Our proposal provides an idea for simultaneously realizing CPB and UPB in the optomechanical system and offers a route for constructing high-quality single-photon sources.
The photon blockade (PB) effect in emitter-cavity systems depends on the anharmonicity of the ladder of dressed energy eigenstates. The recent developments in color center photonics are leading toward experimental demonstrations of multiemitter-cavity solid-state systems with an expanded set of energy levels compared to the traditionally studied single-emitter systems. We focus on the case of N=2 nonidentical quasiatoms strongly coupled to a nanocavity in the bad cavity regime (with parameters within reach of the color center systems), and discover three PB mechanisms: polaritonic, subradiant, and unconventional. The polaritonic PB, which is the conventional mechanism studied in single-emitter-cavity systems, also occurs at the polariton frequencies in multiemitter systems. The subradiant PB is a new interference effect owing to the inhomogeneous broadening of the emitters which results in a purer and a more robust single-photon emission than the polaritonic PB. The unconventional PB in the modeled system corresponds to the suppression of the single- and two-photon correlation statistics and the enhancement of the three-photon correlation statistic. Using the effective Hamiltonian approach, we unravel the origin and the time-domain evolution of these phenomena.