Superconducting Nanowire Single-Photon Detectors Integrated With Current Reservoirs

Superconducting nanowire single-photon detectors(SNSPDs)exhibit high detection efficiency,low dark-count rate,low timing jitter and high photon-counting rate.However,trade-offs exist between detection efficiency and timing characteristics.In order to make the devices simultaneously possess the advantages of high detection efficiency,low timing jitter and fast speed,the research group of Tianjin University proposed the SNSPDs integrated with current reservoirs.In this thesis,theoretical and experimental research on the timing characteristics and device efficiency of the SNSPDs integrated with current reservoirs is carried out.For timing characteristics,the author used electro-thermal model to simulate the performance of the devices.The simulation results show that the SNSPD integrated with current reservoirs can amplify the output pulses,improve the slew rate of the leading edge and reduce the reset time.On the experimental side,the author demonstrated the pulse amplification effect of the current reservoirs,achieved an RFamplifier-free SNSPD system.Compared with the SNSPD without integrating with current reservoirs,the integration of the current reservoirs on a 10μm × 10μm SNSPD reduced timing jitter from 122 ps to 85 ps and reduced the reset time from 11.6 ns to 9.4 ns.For device efficiency,the author simulated the impact of defects on the critical current of the nanowires with different widths.The simulation results show that,compared with superconducting avalanche photodetectors(N-SNAP),SNSPDs integrated with current reservoirs are more immune to defects.The author achieved a device efficiency of 44.7% for a SNSPD integrated with a 300-nm-wide current reservoir,with an active area of 15μm×15μm and the photosensitive nanowire width of 100 nm.As a comparision,the highest reported efficiency for a 4-SNAP that achieved same similar amplification was ~20%.