Frequency dependence of the emission from 2D array Josephson oscillators

Coherent emission from 2-D arrays of Josephson junctions, coupled to a detector junction through a DC blocking stripline capacitor, was detected over a frequency range from 50 to 210 GHz. A power of 0.26 mu W, which is larger than the 0.1 mu W expected from the resistively shunted-junction model, was detected in a range from 140 to 150 GHz. Frequencies where no emission was detected correspond to standing waves in the capacitor when multiples of the half-wavelength match the capacitor length. Low-temperature scanning electron microscopy confirmed the presence of standing waves at these frequencies, but also revealed standing waves at other frequencies, indicating an impedance mismatch and a possible extension of the standing waves into the array.< >