PLASMA-WAVES IN ANISOTROPIC SUPERCONDUCTING FILMS BELOW AND ABOVE THEPLASMA FREQUENCY

We consider wave propagation inside an anisotropic superconducting fil m sandwiched between two semi-infinite nonconducting bounding dieletri c media such that along the c axis, perpendicular to the surfaces, the re is a plasma frequency omega(p) below the superconducting gap. Propa gation is assumed to be parallel to the surfaces in the dielectric med ia, where amplitudes decay exponentially, Below omega(p), the amplitud e also evanesces inside the film. and we retrieve the experimentally m easured lower dispersion relation branch, omega(proportional to)root b eta, and the recently proposed higher frequency branch, omega(proporti onal to)1/root beta. Above omega(p), propagation is of the guided a wa ve type, i.e.: a dispersive plane wave confined inside the film that r eflects into the dielectric interfaces, and the modes are approximatel y described by omega approximate to omega(p) root 1 + (beta/beta(0))(2 ), where beta(0) is discussed hen.