Phase locking of Josephson junctions in a two-dimensional array

Abstract
We studied the behavior of Josephson junctions in a two-dimensional array under the influence of micro-wave irradiation. We are able to distinguish between junctions that are phase locked to the external microwave and unlocked junctions by means of spatially resolving measurements. The degree of coherence in the array can be influenced by tuning the external rf power. Analogies to the coherent behavior of atoms in a laser are pointed out.