Coherent emission from large arrays of discrete Josephson junctions

We observed coherent emission at the frequency of 76 GHz from a large-area array of 7500 niobium junctions embedded in the quasioptical resonator at liquid helium temperature. The maximal detected power of 2 mu W was measured by a room temperature superheterodyne receiver. To explain the coherent behavior of the array of Josephson junctions, electromagnetic field simulations were performed. Considering the substrate as a dielectric resonator antenna, the coherent emission was excited if the locations of each subarray coincided with the positions of the maximum electric field intensity in the substrate resonance mode. c 2009 American Institute of Physics. [doi:10.1063/1.3253417]