(a) The magnitude and (b) phase of the probe transmission versus (Ω – ω₁)/2π when the resonance frequencies of the two mechanical oscillators are different. The insets are the enlarged images in the middle of the figure. The pump field is red detuned by an amount of ω_m = (ω₁ + ω₂)/2 with P_pu = 1 μW. Other parameters are ω_c = 2π × 6.986 GHz, κ = 2π × 6.2 MHz, κ_e = 2π × 4.8 MHz, ω₁ = 2π × 32.1 MHz, ω₂ = 2π × 32.5 MHz, γ₁ = γ₂ = γ_m = 2π × 930 Hz, g₁ = 2π × 39 Hz, g₂ = 2π × 44 Hz.