Electrodynamics of the Josephson-Coupled Parallel Plate Resonator

Eigen oscillations in a superconducting parallel plate resonator with the Josephson-coupled plates are investigated. While the insulator thickness S changes from tens of microns down to the decay lengthscale of the superconducting wavefunction into a dielectric, \xi~1 nm, both the resonant frequency and Q-factor vary non-monotonically by up to three orders in magnitude. A crossover between the Swihart waves and Josephson plasmons causes a global minimum in the resonant frequency and a local maximum in the Q-factor at S~10\xi.