Microwave emission from two-stacked arrays of long Josephson junctions

We have recorded the radiation generated by magnetic flux quanta oscillations and by cavity mode oscillations in two-stacked arrays each consisting of five long Josephson junctions biased in parallel. The two arrays have in common the middle electrode, which is thinner than the London penetration depth, and can be biased independently. Basically, two kind of fluxon states can be generated, one consisting of a row of five fluxons oscillating in one of the arrays, the other consisting of a row of five fluxons in one array and five antifluxons in the other array, bound in a coherent state. It is found from the microwave emission that the latter configuration is less sensitive to low-frequency noise.