Dependences of phases ϕ_1,2 (a–c) and energy transmission coefficients T_1,2 (d–f) of waves 1, 2 on the main layer thickness d₂ for various materials of layers 1, 3. The values of parameters are: ε₁ = ε₃ = 2 + 10⁻³ i (a,d); ε₁ = 2 + 10⁻³ i, ε₃ = 0.01 + 0.01i (b,e); ε₁ = ε₃ = 0.01 + 0.01i (c,f). The values of parameters for all the graphs are: d_1,3 = 0.25 μm, λ = 0.63 μm. Parameter d₂ is used as the abscissa axis for all the graphs.