Effects of microwave radiation on two strongly coupled indium microbridges

Effects of incident microwave radiation on two closely spaced indium micro-bridges are investigated by measuring the current-voltage (I-V) characteristics of the weak links, using microprobes prepared by an electron beam lithography technique. Pronounced distortions as well as negative dynamic resistance are found in the I-V curves where the sum of the two Josephson frequencies is equal to the incident microwave frequency or its harmonics. These results are interpreted in terms of interactions of the weak links with the microwave radiation and with each other via exchange of quasiparticles.