Spectral response of high-quality superconducting point contacts in the presence of background radiation

The dc I-V curves and spectral response of high-quality superconducting point contacts have been experimentally studied. The model of these contacts is suggested to account for their dc properties. These high-quality contacts have a high sensitivity to microwave and background radiation. Spectral response referred to the power absorbed in the contact has been obtained using echellette grating monochromator. Spectral response curves are in qualitative agreement with the theory considering the influence of background radiation on the contact.