EXTERNAL FREQUENCY LOCKING IN SHUNTED BICRYSTAL JOSEPHSON-JUNCTION ARRAYS

Series arrays of 365 shunted YBCO thin film junctions were fabricated on asymmetrical YSZ bicrystals and the frequency locking of different sub-arrays to external microwave power was investigated. Although ther e was a considerable spread in critical currents of the junctions and in the microwave bias current distribution, a first Shapiro step with height of 30% of the total critical current of 39 junctions sub-array was obtained by using an external shunt resistor, thus reducing the sp read in normal resistances to 5%.