600 GHZ RESONANT MODE IN A PARALLEL ARRAY OF JOSEPHSON TUNNEL-JUNCTIONS CONNECTED BY SUPERCONDUCTING MICROSTRIP LINES

The high frequency properties of the one-dimensional transmission line consisting of a parallel array of resistively shunted Josephson tunne l junctions have been studied in the limit of relatively low damping w here this nonlinear system exhibits new and interesting phenomena. Her e we report on experimental investigations of a resonant step observed at a voltage corresponding to 600 GHz in the dc current-voltage chara cteristic of a parallel array of 20 identical small NbAlOxNb Josephson junctions interconnected by short sections of superconducting microst rip line. The junctions are mutually phase locked due to collective in teraction with the line sections excited close to the half wavelength resonance. The phase locking range can be adjusted by means of an exte rnal dc magnetic field and the step size varies periodically with the magnetic field.