Absorption, dispersion, group index, and delay/advance time versus Δp/Γ such that γ41 = 1Γ, γ21,32,43 = 0.02Γ, ω0 = 103Γ, Ω1 = Ω3 = 1Γ, Δ1 = Δ3 = 0Γ, VD = 20Γ, η1 = η3 = 1.