Abstract
In this paper, we study the unconventional photon blockade of symmetric and antisymmetric modes in a photonic molecule system with bilateral drive. We show that the photon blockade effect is controllable by manipulating the tunnelling strength of two cavities and the ratio of driving strengths. Under the weak driving condition, we present the exact optimal conditions for strong antibunching photons. The optimal conditions are in good agreement with the numerical results. It is also found that the optimal value of detuning frequencies is not sensitive to the value of the ratio to achieve the unconventional photon blockade effect. The feasibility of tunable unconventional photon blockade effect also has been studied based on the experimental parameters. Our studies of the photonic molecule system can be used as a single-photon source based on the symmetric and antisymmetric modes in the regime of weak nonlinearity.