A Novel High-Speed Photon Counting System with Programmed Dead Time

With high sensitivity at single photon level, Geiger-Mode (GM) avalanche photodiodes (APD) are widely used in spectrum measurement, 3D imaging, astronomical observation, biomedical and other fields. In this paper, a high-speed photon counting system is proposed with an active quench and reset integrated circuit (AQR-IC) that drives a near infrared InGaAs GM-APD. The avalanche current is converted into voltage signal by utilizing parasitic capacitance of APD and circuit's input port. Multi-stage inverters detect the induced voltage, and generate an output TTL pulse indicating occurrence of avalanche event. At the same time, the active quench circuit is introduced to stop avalanche quickly. Then the active reset circuit makes APD working in Geiger mode after a programmable delay time which could be set by field programmable gate array(FPGA). The adjustable dead time enormously improve the flexibility of photon counting system applications. The proposed AQR-IC was fabricated in SMIC 0.18 μm CMOS process. Applied for InGaAs GM-APD, experimental results show that the circuit is capable of fast quenching and recovering. The system provides adjustable dead time from 64 ns up to 163.6 μs with a setting resolution of 20 ns, corresponding to a maximum counting rate of 15.6 MHz. The system can meet the application requirement of free-running mode detection.