“…In fact, in the case ␦ A ϵ␦ B ϭn , the half-wavelength condition is satisfied at every layer, so that Q A ϭI and Q B ϭ(Ϫ1) n I, and the transparency condition Tϭ1 is trivially obtained. 19,20,[22][23][24]31,32 Analogously, in the case ␦ B ϭn , we get Tϭ1 for any  as well. In this case the two-component FDM will behave like an equivalent homogeneous periodic medium, characterized by an effective thickness dЈϵ(pϩq)d A and a refraction index n A .…”