FISKE RESONANCES IN WINDOW JOSEPHSON TUNNEL JUNCTIONS

We report experimental data about the Fiske step voltages in window Josephsonjunctions showing that the phase velocity of electromagnetic waves is strongly af- fected by the insulating region surrounding the junction. We have investigated sep- arately in unidimensional junctions the effect either of an idle region along the long dimension or at the extremities of the junction, finding that the former increases the phase velocity and causes dispersion, the latter only decreases the velocity. We propose two simple models to account for these phenomena.