Collective modes in superconductor-dielectric photonic crystals

On the basis of the linear response theory we calculate the components of the electromagnetic propagator of a periodic non magnetic one dimensional system, consisting of alternating superconductor- dielectric slabs of different thicknesses. The photonic band structure and the corresponding power spectra are studied from the poles and the imaginary part of the electromagnetic propagator. It is shown that, for a given lattice period, when the superconducting slab occupies a major percentage of the unitary cell of the photonic crystal, the number of bands in a fixed range of frequencies diminishes, the intervals of forbidden frequencies decrease and the respective allowed bands present a strong dependence with the wave quasivector. Additionally, as well as the London penetration length decreases, the bands become less dispersive, which indicates the role played by the superconductor slabs in the coupling of neighbour unit cells.