Josephson junctions fabricated by focused ion beam.

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Large Area Superconducting Nanowire Single Photon Detector Arrays

Superconducting Nanowire Single Photon Detectors (SNSPDs) are a promising emerging technology for high efficiency single infrared photon detection. Excellent signal-to-noise ratio, high efficiency and good timing resolution can currently be achieved in small single pixel SNSPDs (area smaller than 14×14 μm2). This small area is a severe practical limitation for emerging infrared photon counting applications requiring multimode fibre or free space optical coupling. In this paper we demonstrate fabrication and full optical testing of an array of 2×2 SNSPDs, using nanowires in parallel configuration, covering an active area of 30 × 30 μm2. We report a system detection efficiency (~ 2.6 % @ λ=1550 nm) and low timing jitter (FWHM ~ 70 ps). Moreover, advanced nano-optical characterization, using an innovative cryogenic miniature confocal microscope, enabled us to confirm the high uniformity of patterned nanowires across the entire sensitive area of the SNSPD array