Self-radiation power and microwave coupling of YBCO Josephson junction arrays on bicrystal MgO substrates

We have studied the microwave properties of the Josephson junction array by measurement of Josephson self-radiation power and Shapiro-steps. The serial–parallel and parallel Josephson junction arrays were prepared with and without additional inductive coupling lines. The maximum detected power of 22 GHz from the serial–parallel array is about 25 pW and its peak point revealed a good quality of frequency-locking and exactly satisfied the Josephson voltage–frequency relationship. Although the parallel array has similar physical properties of average critical current and normal resistance of Josephson junctions to serial–parallel array, the maximum detected power is only about several tens of fW. The received power of serial–parallel array is higher than that of the parallel array for the same intensity of irradiation power.