Propagation constant - Limited surface modes in dielectric superlattices

The surface modes of a dielectric superlattice - their very existence - depend strongly on the position of the surface (the cut-plane through the last cell). For example, TE and TM surface waves can propagate even when the layer next to the surface is made of lower-index material. In this case we find a novel TE mode where the propagation constant is limited by a bulk band. For TM polarization, the propagation constant may be limited due to a different mechanism, namely the internal (within the dielectric layers epsilon(a), epsilon(b)) Brewster effect. This upper bound is k(0)[epsilon(a) epsilon(b)/(epsilon(a) + epsilon(b))](1/2), where k(0) is the vacuum propagation constant.