Fig. 1. Structure of SnV color center system and the equipment diagram of optical bistability. (a) Atomic structure of SnV color center; (b) electronic structure of SnV color center; (c) schematic of N-type four-level scheme with a probe field (Ω_p) and two coupling fields (Ω_c,Ω_d); (d) unidirectional ring cavity with four mirrors containing the SnV centers' sample of length L. M₃ and M₄ represent total mirrors;

Fig. 2. Influence of probe frequency detunings Δ_p on optical bistability. (a) Output field x versus input field y for different prob

Fig. 3. Influence of coupling frequency detunings Δ_c on optical bistability. (a) Output field x versus input field y for different c

Fig. 4. Influence of coupling field strength Ω_c on optical bistability. (a) Output field x versus input field y for different coupli

Fig. 5. Influence of coupling field strength Ω_d on opticical bistability. (a) Output field x versus input field y for different coup

Fig. 6. Output field x versus input field y for different cooperation parameters. Other parameters are Ω_c=4γ,Ω_d