Enhanced photon blockade in an optomechanical system with parametric amplification

We propose a scheme to enhance the single- and two-photon blockade effects significantly in a nonlinear hybrid optomechanical system with optical parametric amplification (OPA). The scheme does not rely on strong single-photon optomechanical coupling and can eliminate the disadvantages of suppressing multi-photon excitation incompletely. Through analyzing the single-photon blockade (1PB) mechanism and optimizing the system parameters, we obtain a perfect 1PB with a high occupancy probability of single-photon excitation, which means that a highquality and efficient single-photon source can be generated. Moreover, we find that not only the two-photon blockade (2PB) effect is significantly enhanced, but also the region where2PBoccurs is widened whenOPAexists, wherewe also derive the optimal parameter condition to maximize twophoton emission and higher photon excitations intensely suppressed at the same time.