Fig. 1. (a) Energy level structure of tripod-type four-level atomic system; (b) position relationship between probe, coupling and signal beams and atomic system, where the 0th and 1st order diffraction directions are indicated

Fig. 2. Amplitude and phase of transmission function T(x) versus x (Δp=2.4γ,Δc=0, Δs=0.24γ, Ωp=0.1γ, L=920,M=5, Λ/λp=4, γ41=γ42=γ43=γ, γ32=γ31=γ21=0.04γ, Г41=Г42=Г43=0.66γ).(a) T=0 K, Ωc=13.6γ, Ωs=0.19γ; (b) T=300 K, Ωc=17.7γ, Ωs=0.28γ

Fig. 3. Diffraction intensity versus sin θ with and without phase modulation. (a) T=0 K, Ωc=13.6γ, Ωs=0.19γ; (b) T=300 K, Ωc=17.7γ, Ωs=0.28γ

Fig. 4. First-order diffraction intensity IP(θ1) as a function of Ωc and Ωs with different L(T=0 K, Δc=0, Δp=2.4γ, Δs=0.24γ). (a) L=100; (b) L=300; (c) L=600; (d) L=920

Fig. 5. First-order diffraction intensity IP(θ1) as a function of Ωc and Ωs with different L (T=300 K, Δc=0, Δp=2.4γ, Δs=0.24γ). (a) L=100; (b) L=300; (c) L=600; (d) L=920

Fig. 6. First-order diffraction intensity IP(θ1) as a function of Δp and Δs with different temperatures (L=920, Ωc=12.03γ, Ωs=0.19γ). (a) T=0 K; (b) T=300 K