Detected power and linewidth of Josephson self-radiation from frequency-locked and microwave-coupled arrays in a waveguide detection system

Frequency-locked and microwave-coupled arrays of high- superconducting Josephson junctions have been developed. The Josephson junctions were prepared on bicrystal MgO substrates using a pulsed laser ablation method. The maximum detected power of Josephson self-radiation, which is directly detected by a superheterodyne receiver with a central frequency of 22 GHz, from the arrays was enhanced with increasing number of Josephson junctions. The Josephson self-radiation properties of the arrays revealed a good quality of frequency locking and exactly satisfied the Josephson voltage-frequency relationship. A narrower linewidth of the Josephson self-radiation was obtained by increasing the number of Josephson junctions in the array.