Unbiased Josephson junction microwave parametric amplifier - experiment

Parametric amplification using unbiased Josephson junctions has been previously reported by several investigators. In the present experiments, the nonlinear, active element consists of a series of unbiased Anderson-Dayem microbridges. The amplifier was operated in the 'doubly degenerate' mode, with pump (at ω0), signal (at ω1) and idler (at ω2) closely spaced in frequency according to the relation 2ω0=ω1+ω2. Eighty (80) series-connected junctions, spaced 5μm apart, were fabricated in a 1000A tin (Sn) film by an intersecting scratch technique described by Chiao et al. Typical bridge dimensions were 0.3μm x 0.3μm and were spaced 5μm apart. (Auth.)