  The conventional photon blockade for high-frequency mode is investigated in a
two-mode second-order nonlinear system embedded with a two-level atom. By
solving the master equation and calculating the zero-delay-time second-order
correlation function $g^{(2)}(0)$, we obtain that strong photon antibunching
can be achieved in this scheme. In particular, we find that by increasing the
linear coupling coefficient of the system, a perfect blockade region will be
formed near the zero second-order nonlinear coupling coefficient. Similarly, by
increasing the nonlinear coupling coefficient of the system, the perfect
blockade zone will appear. And this scheme is not sensitive to the reservoir
temperature, both of which make the current system easier to implement
experimentally.
