Temperature dependence of submillimeter wave response in the point-contact Josephson junction

The temperature dependence of the sub-mm wave response in two types of point-contact Josephson junctions (a bridge-type and a tunnel-type) was measured by minutely varying the temperature according to a fixed frequency. The ac power source for the measurements was a sub-mm wave laser operating at wavelengths of 699, 570, and 469 microns, respectively. The temperature dependence of the sub-mm wave response was fitted to predictions from tunnel junction theory. The damping factors obtained from the measurements were 0.02 and 0.05 for the tunnel-type and bridge-type junctions, respectively. The existence of a Riedel peak at the normalized frequency was confirmed.