Characterisation of Josephson junction bolometers by a fiber coupled system

摘要

Nb/Al-AlO_x/Nb Josephson junctions used as bolometers have been characterised by illuminating them with laser light at λ = 690 nm. The influence of different parameters of the detector on its overall behaviour has been considered. The characterization has been done with a dedicated system based on piezoelectric micropositioning of an optical fiber, suitable to work in vacuum and at 4.2 K. This system allows one to control the distance of the fiber from the sample, while the sensitive surface of the detector is scanned by the combined action of four piezoelectric bimorphs.