The bistable behavior of the intra-cavity photon number |c_s|² is shown versus the amplitude of the driving field E_L for several masses of NMR₁ (NMR₂). (a) The black, blue, orange curves represent the bistable information for m₁ = m₂, m₁ = 1.2m₂, and m₁ = 1.5m₂, respectively. (b) The several colors represent the variation in photon intensity for various frequencies, i.e., ω₁ = 0.9ω₂, 1.0ω₂, and 1.2ω₂. Other parameters are counted as ω_1,2/2π = 947 kHz, κ/2π = 215 kHz, g_c/2π = 100 kHz, g/2π = 10 kHz, Δ_a/2π = 20 kHz, and Δ_c = 3κ.