Radio-frequency spectral response of two-dimensional Josephson-junction arrays

Abstract

The spectral response of rf-biased planar arrays of 300\ifmmode\times\else\texttimes\fi{}300 Nb-Au-Nb proximity-effect junctions is reported over the frequency range 10--400 MHz in zero magnetic field. The response consists of narrow-bandwidth emissions at both harmonics and subharmonics of the rf bias frequency. In contrast to the harmonic signals, which vary smoothly with dc bias current, the subharmonic signals appear only when the array is biased on specific giant Shapiro steps.