Fizeau's interferometer device in thin superconducting films

We propose here that thin superconducting lms, deposited on a substrate of high dielectric constant, be used in Fizeau's experiment, which probes how light propagates inside a drifting charged condensate. We predict that the phase shift of the propagating light is well described by an effective Lond on length, and is proportional to v(0)/(w/k), where v(0) is the superfluid velocity and w/k the phase velocity of the propagating mode. We claim that YBa2Cu3O6+x thin lms grown on SrTiO3 form a system where this phase shift i s large enough to be measured.