Coupled surface states in one- and two-dimensional frequency dependent photonic crystals

One-dimensional photonic crystals with a frequency dependent material such as a metal or a polaritonic substance have very interesting properties. Their band structure can be calculated by a Kronig-Penney like equation where one uses next to the Bloch condition the continuity of the field and its derivative. The bulk absorption behaviour can be observed in the band structure as well but the size of the band gap is decreased proportional to the thickness of the frequency dependent layers. These absorption band gaps are complete for both polarisations and all angles of incidence except for modes propagating parallel to the surface. In this work these surface solutions are compared with ordinary surface plasmons and polaritons propagating on a simple metal/polaritonic to air interface. The band structure calculation of a two-dimensional frequency dependent photonic crystal is much more complicated. For a metallic photonic crystal flat bands occur in the band structure for a certain polarisation which are the surface plasmon (Mie) resonances. We show resulting the field enhancement by calculating the local density of states. Furthermore we investigate the band gap for the second polarisation and design a W1 wave-guide to demonstrate the localisation of the electromagnetic field.