Observation of microwave synchronization of thin film microbridge arrays

We report on the characteristics of thin film microbridge Josephson junctions fabricated using electron beam lithography and discuss the techniques used to fabricate these junctions, which are typically 0.3μ square. Extensive measurements have been made on both individual junctions of tin and indium and on small arrays of these junctions. Synchronization of current biased series arrays by an applied microwave field has been achieved. This synchronization appears as a zero differential resistance across the entire array at a voltage of MVJwhere M is the number of elements in series and VJis the Josephson voltage hv/2e. Furthermore we have observed a systematic variation with microbridge dimension of the microwave enhancement of the critical current.