Fabry–Perot filters with tunable Josephson junction defects

• We propose a tunable filter exploiting Josephson junctions nonlinear inductance.
• The resonance center frequency is tuned by the external current.
• The long Josephson junctions features are within fabrication feasibility.
• The full wave analysis of the defect agrees with the linearized approximation.

We propose to take advantage of the properties of long Josephson junctions to realize a frequency variable Fabry–Perot filter that operates in the range 100–500 GHz with a bandwidth below 1 GHz. In fact, we show that it is possible to exploit the tunability of the effective impedance of the Josephson component, that is controlled by a dc bias, to tune, up to 10% of the central frequency, the resonance of the system. An analysis of the linearized system indicates the range of operation and the main characteristic parameters. Numerical simulations of the full nonlinear Josephson element confirm the behavior expected from the linear approximation.