Singularities of an I-V Curve and Voltage Fluctuations in “Ideal” Superconducting Nb Point Contact

A method of constructing a point contact Josephson device with “ideal” I - V characteristics is described. Radio frequency (RF) outputs are detected with no intentionally applied external RF fields. Enhancements of output RF intensities occur at the gap and sub-gap voltages. Strong sharp peaks of RF outputs of approximately 10 -12 W are observed at lower voltage regions. Effects of thermal and shot noises are discussed in relation to the singularities of an I - V curve.