13 May 2015 Large-area NbN superconducting nanowire avalanche photon detectors with saturated detection efficiency
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Superconducting circuits comprising SNSPDs placed in parallel—superconducting nanowire avalanche photodetectors, or SNAPs—have previously been demonstrated to improve the output signal-to-noise ratio (SNR) by increasing the critical current. In this work, we employ a 2-SNAP superconducting circuit with narrow (40 nm) niobium nitride (NbN) nanowires to improve the system detection efficiency to near-IR photons while maintaining high SNR. Additionally, while previous 2-SNAP demonstrations have added external choke inductance to stabilize the avalanching photocurrent, we show that the external inductance can be entirely folded into the active area by cascading 2-SNAP devices in series to produce a greatly increased active area. We fabricated series-2-SNAP (s2-SNAP) circuits with a nanowire length of 20 μm with cascades of 2-SNAPs providing the choke inductance necessary for SNAP operation. We observed that (1) the detection efficiency saturated at high bias currents, and (2) the 40 nm 2-SNAP circuit critical current was approximately twice that for a 40 nm non-SNAP configuration.
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Ryan P. Murphy, Ryan P. Murphy, Matthew E. Grein, Matthew E. Grein, Theodore J. Gudmundsen, Theodore J. Gudmundsen, Adam McCaughan, Adam McCaughan, Faraz Najafi, Faraz Najafi, Karl K. Berggren, Karl K. Berggren, Francesco Marsili, Francesco Marsili, Eric A. Dauler, Eric A. Dauler, "Large-area NbN superconducting nanowire avalanche photon detectors with saturated detection efficiency", Proc. SPIE 9492, Advanced Photon Counting Techniques IX, 94920E (13 May 2015); doi: 10.1117/12.2178322; https://doi.org/10.1117/12.2178322

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