Frequency Dependence of the Submillimeter-Wave Response in the Tunnel-Type and Bridge-Type Josephson Junctions

Abstract
We have fabricated ultrasmall tunnel-type Josephson junctions with Nb–SnO x –Sn film point-contacts. Using these junctions, we have measured for the first time the Shapiro steps in the submillimeter-wave region and have compared the strength of steps of this junction with that of the bridge-type Nb–Sn ingot point-contacts. We found that the tunnel-type junction shows a sharper Riedel peak than the bridge-type junction.