Microwave mixing with niobium variable thickness bridges

Niobium thin-film bridges 300 Å thick, 1 μm wide, and 0.5 μm long joining two bulk films 5000 Å thick and having normal resistance of ∼1 Ω have been fabricated and used for microwave mixing at 10 GHz. They exhibit Josephson, bolometric, and multiple-flux-flow mixing and have useful response at 100–200 GHz. The data show in a direct way limitations imposed by flux flow and heating.