APD单光子计数的主动抑制系统

Active-quenching system on APD single-photon count

设计了一种主动抑制系统,用以控制APD在单光子计数检测时的死区时间。该系统主要利用ECL(射随耦合逻辑)电平电路对雪崩脉冲进行快速甄别从而判断光子到来与否,再将比较器输出的脉冲通过整形处理输出给延时电路,利用CPLD搭建延时电路,输出两路延时脉冲,两路延时脉冲分别输出给主动抑制电路和快恢复电路,以完成APD死区时间的控制。此主动抑制系统,有效地将死区时间缩短在45 ns;将光子计数率提高到20 MHz。

An active-quenching system is designed to control the dead time of Avalanche Photon Diode （APD） in signal photon counting detecting. The system mainly uses ECL （Emitter coupled logic） level circuit to compare with avalanche pulse quickly and determine whether the photon is coming or not,and then output the pulse of the comparator and shape it to the de-lay circuit. Using CPLD set up the delay circuit,two delay pulses are output to the active-quench circuit and fast reset circuit re-spectively to control the dead time of the APD. The active-quenching system could shorten the dead time to 45 ns effectively, and increased photon count rate to 20 MHz.