微型化自由运行InGaAs/InP单光子探测器(特邀)

单光子探测器具有最高的光探测灵敏度，在激光雷达系统中使用单光子探测器可以极大提升系统的综合性能。近红外二区(1.0～1.7μm)激光具有大气透过率高、散射弱、太阳背景辐射弱等优势，是大气遥感、三维成像等激光雷达系统的理想工作波段。研制了一种基于InGaAs/InP负反馈雪崩光电二极管的微型化自由运行单光子探测器。该探测器长宽高为116 mm×107.5 mm×80 mm，在1.5μm最大探测效率超过35%，时间抖动(半高宽)低至80 ps。为满足激光雷达系统对光子飞行时间测量的需求，探测器内部集成时间数字转换(TDC)功能，时间精度100 ps。同时，探测器集成一套后脉冲修正及计数率修正算法，可以有效降低探测器所引起的雷达信号畸变。

Miniaturized free-running InGaAs/InP single-photon detector (invited)

  Objective  Single-photon detectors have the highest sensitivity of light detection. The utilization of single-photon detectors in LiDAR system can greatly improve the comprehensive performance of the system. Laser in the second near-infrared region (1.0-1.7 μm) has the advantages of high atmospheric transmittance, weak scattering and weak solar background radiation, which is the ideal working band of aerosol remote sensing and three-dimensional imaging LiDAR system. Therefore, a high-performance miniaturized free-running single-photon detector is designed in this paper.   Methods  The single-photon detector is based on InGaAs/InP negative feedback avalanche photodiode (NFAD), allowing it to operate in the free-running mode (Fig.1). A precise bias circuit and a precise temperature control circuit provide the bias voltage and cooling for the NFAD, respectively (Fig.2, Fig.3). In order to meet the needs of photon time-of-flight measurement for LiDAR system, the time-to-digital converter (TDC) function is realized by FPGA based on carry delay chain (Fig.4). Through the built-in micro controller unit (MCU) with integrated counting rate and afterpulse correction algorithm, it can make real-time correction of TDC data and output via USB interface.   Results and Discussions   The detector has dimensions of 116 mm×107.5 mm×80 mm (Fig.5). The maximum detection efficiency is more than 35% at 1.5 μm (Fig.6), and the time jitter (full width at half maxima, FWHM) is as low as 80 ps (Fig.7). The time measurement accuracy of internal TDC can reach 100 ps. The miniaturized LiDAR product using this single-photon detector can detect up to 15 km with a range resolution of less than 30 m (Fig.8).   Conclusions  The QCD600 series miniature free-running InGaAs/InP single-photon detector provides a compact and real-time data post-processing single-photon detection solution for LiDAR systems in the near infrared band with high efficiency, low noise, low time jitter. In the future, free-running single-photon detector will be developed in the direction of miniaturization using integrated refrigeration technology and ultra-low noise using deep refrigeration technology, which will provide more powerful technical support for LiDAR, QKD and other applications.