Millimeter-wave Josephson Radiators

We describe the design and characterization of mm-wave radiators driven by the ac Josephson effect. Each radiator consists of a microstrip patch antenna driven by a voltage-biased Josephson junction; the radiator emits coherent free-space photons at well-defined frequency and polarization. The photon frequency and emitted power can be tuned by appropriate variation of the junction parameters and antenna dimensions. We present the results of numerical simulations that have informed antenna design and material choice, and we compare against measurement results. We discuss the suitability of these radiators for the calibration of sensors for astrophysical and rare event detection.