中文摘要：

超导纳米线单光子探测器（SNSPD）是一种新型单光子探测器,具有灵敏度高、时间精度高、探测速度快和暗计数低等特点,在激光测距等领域具有重要应用前景.本文将SNSPD应用到1064 nm波段激光测距系统,研究了其暗计数和信噪比对激光测距的影响.基于实验获得的回波数据,结合激光雷达理论,研究了系统信噪比与脉冲积累次数的关系.分析表明,SNSPD暗计数是影响测距距离的关键因素之一.结合仿真,进一步探究了基于SNSPD的激光测距系统信噪比与回波率、暗计数的关系,暗计数较大时,信噪比随脉冲积累次数增加出现波动现象,回波信号湮没.由于SNSPD暗计数极低,本基于SNSPD的测距系统最远测距可达280 km,较同样条件下基于APD探测器的测距系统最远探测距离远40 km,在军事侦查、探测和制导等领域具有重要应用前景.

英文摘要：

Superconducting nanowire single photon detector（SNSPD） is a competitive candidate in laser ranging at 1064 nm wavelength compared with other single photon detectors such as InGaAs/InP APD for its high sensitivity,high time precision and low dark counts.In this paper,we apply our SNSPD to a laser ranging system measuring target in Qinghai lake area with atmospheric scatter.The echo photons are received by telescope,and transport through the multimode fiber to the SNSPD photon-sensitive area.The SNSPD,integrated in an optical cavity with a resonant wavelength of1064 nm,is fabricated on a MgF_2 substrate.The optical absorption of Nb N film goes up to 98% according to FDTD simulation,and the system efficiency is measured to be about 40%.A pulsed laser at 1064 nm,featuring a peak power of 12 MW and a pulse width of 10 ns,is adopted in the laser ranging system.In this experiment,we first measure the system intrinsic noise and the environment noise introduced into the laser ranging system after turning off the laser.After that,we measure the echo rate for the target at 126 km,which increases up to 96% with an attenuator of 10 d B at the receiver side.The maximum distance of the laser ranging system is analyzed based on the experimental results of dark count and echo rate through a theoretical model of laser radar.The analysis indicates that signal-to-noise ratio（SNR） is increased smoothly with the accumulation of time.At the same time,we simulate how the dark counts influence the capability of laser ranging system based on SNSPD,the simulated SNR matches well with the experimental data of target at 126 km.Furthermore,the dark counts,accumulation of time and probability of echo photon affect the SNR according to the simulation results,showing that large dark counts would result in SNR fluctuation and signal annihilation when the probability of echo photon is low.Thus,the maximum distance of laser ranging under the assumption of integration time is estimated through the SNR simulated result,showing that a maximum