kx_m = n1·sinθ + m·λ/Λ TE: PQ = KX² − E → λ² = eig(PQ) TM: S = Einv^(−1/2)·(I − KX·Einv·KX)·Einv^(−1/2) → μ = eig(S) X = exp(−λ·d·k0) S_casc = Redheffer( S_A , S_B )