The display of the FWM intensity versus the dimensionless frequency δ/ω₁ for different values of optomechanical coupling g₀ for the cases: (a) both atom field coupling and Coulomb coupling are zero, i.e., g = 0 and g_c = 0; (b) g = 0 and g_c ≠ 0; (c) g ≠ 0 and g_c ≠ 0. Other parameters are γ₁ = ω₁/Q, γ_a/2π = 0.1 kHz, g_c/2π = 100 kHz, κ/2π = 215 kHz, g/2π = 10 kHz, and E_L = 2π × 20 MHz.