Parametric interactions in high-T/sub c/ superconducting step edge junctions at X-band

The authors have fabricated and tested both single junctions and series arrays of YBCO step edge junctions for four photon parametric effects at X band as a first step in developing a parametric amplifier at 60 GHz. The series array of 25 junctions at 10.3 GHz shows a 10-dB increase in reflected signal power as the pump power is increased, while the single junction at 12.2 GHz indicates a 2-dB change. The reflected power at the characteristic idler frequency of 2 omega /sub p/- omega /sub s/ is evidence of true Josephson junction parametric interaction. The use of thallium-based films at 60 GHz, which offer a broader range of operating temperatures than does YBCO, is currently being investigated. The design being considered for a parametric amplifier at V band is a combination of microstrip-based series arrays of junctions and an antipodal finline transition.<>