  This paper discusses conventional photon blockade (CPB) and two-photon
blockade (2PB) in a three-wave mixing system embedded with a two-level atom in
the high-frequency cavity. Analytical conditions for achieving CPB and 2PB are
obtained by analyzing the eigenvalues of the system Hamiltonian. Numerical
solutions, derived by solving the master equation in a truncated Fock space,
are consistent with the analytical conditions. Detailed analysis of system
parameters reveals the influence of the embedded atom on achieving different
types of photon blockade. Unlike previous schemes, this system can achieve
single-photon blockade simultaneously in three photon modes. Additionally, by
adjusting the coupling coefficient between the atom and high-frequency mode
photons, the system can switch between single-photon blockade and two-photon
blockade in the high-frequency mode.
