Millimeter-wave Josephson Radiator Arrays

We describe the development of arrays of mm-wave radiators based on the ac Josephson effect. The individual elements of the array are aperture antennas incorporating voltage-biased Josephson junctions. Each element provides a coherent source of narrowband photons with well-defined polarization. For appropriate antenna and junction parameters, it is possible to achieve near unit coupling to free space at the antenna resonance. Arrays of elements provide a means to enhance the emitted power in a chosen direction and to suppress emission in the plane of the array. We present the results of numerical simulations that have guided material choice and array design, and we describe characterization of various array prototypes. We discuss application of these arrays to the calibration of sensors for astrophysical and rare event detection.