HTS detectors based on Josephson nano Junctions

T. WOLF; J. LESUEUR; M. SIRENA; P. FEBVRE; G. FAINI; J. BRIATICO; R. BERNARD; N. BERGEAL

Chicago, USA

Conferencia; Applied Superconductivity Conference, ASC 2008; 2008

There is a strong need of highly sensitive photons detectors in the range of a few 100 GHz to a few THz for security systems, airborne vision or molecule detection for instance. Josephson Junctions are potentially a very attractive solution since they can reach very high efficiencies close to the quantum limit. High Tc Superconductors (HTS) have the advantages of a wide gap which allows detection far in the THz range, and rather simple cryogeny (77 K). HTS Josephson nano-Junctions made by ion irradiation exhibit interesting features for these applications, such as easily tunable parameters, high critical current densities, reasonable IcRn products, but, above all, good reproducibility and scalability. Starting from a c-axis YBCO film, a device including a wide band antenna coupled to a microbridge is designed using a first step of 100 keV oxygen irradiation with a fluence of 5 10^15 at/cm2. A nano-Junction is then made in the middle of the bridge using a fluence of a few 10^13 at/cm^2. The fluence is chosen for an operating temperature ranging from 4 K to 77K. The size of the antenna corresponds to frequencies in the 100 GHz range. Direct detection of photons with a single junction is presented, together with noise performances. Extension to arrays of junctions will be shown.