(a) Energy-level structure of the hybrid optomechanical system, where the states of the levels are ∣ i 〉 (i = 1, 2, 3, 4). The amplitude of the external mechanical driving field is ε d . The energy differences between ∣ 1 〉 and ∣ 4 〉 , ∣ 1 〉 and ∣ 2 〉 , and ∣ 1 〉 and ∣ 3 〉 are the frequencies of cavity a, mechanical resonator b, and mechanical resonator c, which are ω a , ω b , and ω c , respectively. ω pr is equal to ω a , and the detuning events between them are ω pr − ω pu = ω b = ω c . (b) Energy-level structure of the hybrid optomechanical system in the dressed-state picture, with the relation ω b = ω c = ω m . ∣ λ ± 〉 are the new dressed levels generated by the coupling effect between the mechanical resonators, with an energy difference of 2J.