Experimental study of a harmonic mixer based on a series chain of YBaCuO bicrystal Josephson junctions in zero-bias operation

Sequential chains of HTS Josephson junctions with an optimized log-periodic antenna operating in the THz signal mixing regime have been calculated, manufactured and measured. It is shown that the synchronous operation of the junctions leads to an increase in the integral absorbed power and, as a result, an increase in the dynamic range. Two regimes were found: at low temperatures, coordinated excitation of junctions in the chain is observed, at high temperatures, “giant” Shapiro steps appear, indicating synchronization of junctions. The characteristics of the mixer have been studied using the mixing operation with the higher harmonics of the heterodyne signal. For an optimal pumping level with a frequency of 3 GHz, a non-zero amplitude of the intermediate frequency was detected when mixed with a 120 GHz signal at 40 harmonics. It is shown that in the optimal regime of operation of the mixer, the configuration of the series chain allows the use of the zero offset regime.