Design of a Real-Time Afterpulsing Monitoring Circuit for Single Photon Avalanche Diode

In this work, a real-time afterpulsing monitoring circuit for single photon avalanche diode (SPAD) is proposed and implemented which can be used in real-time to detect the afterpulsing probability in SPAD. The circuit is based on passive quenching circuit, monostable multivibrator and FPGA and can be used for SPAD with different bias voltages (Vb). To evaluate the designed circuit, a Si SPAD, previously developed was used with an operating bias voltage of approximately 25.6V. Experimental results show that the afterpulsing effect measured using the circuit developed is very close to that measured using a TDC (Time-to-Digital Converter) instrument. The measurement differences are below 11% as the increasing of the bias voltage. The circuit developed is simple, compact and can be used to monitor the real time afterpulsing for any SPAD that enables the real-time intelligent control for maintaining a reasonable afterpulsing propobility in SPAD based photon counting system.