ObjectiveThe single-photon source is the essential resource in the fields such as quantum communication, quantum computing, and quantum cryptography, while photon blockade is an important means of preparing single-photon sources and controlling single photon. The photon blockade effect in optomechanical systems has been receiving wide attention and was studied intensively. The Kerr nonlinear interaction between photons induced by optomechanics is just the main mechanism for generating photon blockade. This paper aims to realizing photon blockade in a fully coupled hybrid cavity opto-mechanical system consisting of a cavity opto-mechanical system and a two-level atom with three subsystems coupled to each other, where photon blockade effect occurs. It is of great significance for the preparation of single-photon and two-photon sources.MethodsThe Hamiltonian of the system consists of three parts: the free Hamiltonian, the interaction Hamiltonian and the driving Hamiltonian. We treat the Hamiltonian of the system by applying the Schrieffer-Wolff approximation to the Hamiltonian of the system, the three-body system can be approximated as two-body system of cavities and mechanical oscillators, and we obtain a fully diagonally effective Hamiltonian and its eigen systems. Although the three-body system is transformed into a two-body system, the transition frequency of the two-level atom plays an important role, which induces a shift in the cavity resonance frequency. There exist two detunings in the system, the cavity field detuning and the drive detuning, which affect the frequency of the cavity field, thus the system has two adjustable parameters to regulate the photon blockade effect. The Kerr nonlinear term leads to the anharmonicity of the energy levels which is the essential cause of the photon blockade.Results and discussionsWe perform accurate numerical simulation by means of the master equation comparing it with the analytical solution. We find that photon blockade occurs when both detunings are adjusted. The analytical results and the numerical results are in good agreement. At some cavity field detuning the two-photon blockade regime becomes wider when increasing the driving intensity. At some drive detuning the photon blockade has a small effect when increasing drive intensity. For weak driving the photon blockade depends mainly on the detuning rather than the driving intensity.ConclusionsIn this paper, we studied single- and two-photon blockade in the fully coupled cavity opto-mechanical system. After an unitary transformation a fully diagonal effective Hamiltonian can be obtained. Enhancement of the optical-mechanical coupling constant can be realized by adding a two-level atom to the system. A Kerr nonlinear term comes up in the Hamiltonian which constructs the conditions for the creation of photon blockade. It can be observed from the Hamiltonian that the system has two adjustable detuning respect to the resonant frequency of the cavity. Then we investigate the photon blockade of the system under the different detuning and driving strength using the probability amplitude equation method and the quantum master equation method, and the both results of which are in good agreement. The results of the study provide new options for obtaining single- and two-photon sources.