Realizing a Robust, Reconfigurable Active Quenching Design for Multiple Types of Single-Photon Avalanche Detectors

TL;DR

This paper introduces a reconfigurable, robust hybrid active quenching circuit for single-photon avalanche detectors, enabling flexible, remote control and field calibration suitable for space applications and diverse APDs.

Contribution

The paper presents a novel System-on-Chip based design combining FPGA and microcontroller for adaptable, field-adjustable active quenching of various APDs, reducing development time and costs.

Findings

Operates a commercial APD at -20°C with 35ns deadtime

Maintains after-pulsing probability near 3%

Demonstrates versatility with custom chip-scale APDs

Abstract

Most active quench circuits used for single-photon avalanche photodetectors (APDs) are designed either with discrete components which lack the flexibility of dynamically changing the control parameters, or with custom ASICs which require a long development time and high cost. As an alternative, we present a reconfigurable and robust hybrid design implemented using a System-on-Chip (SoC), which integrates both an FPGA and a microcontroller. We take advantage of the FPGA's speed and reconfiguration capabilities to vary the quench and reset parameters dynamically over a large range, thus allowing our system to operate a variety of APDs without changing the design. The microcontroller enables the remote adjustment of control parameters and calibration of APDs in the field. The ruggedized design uses components with space heritage, thus making it suitable for space-based applications in the fields of telecommunications and quantum key distribution (QKD). We demonstrate our circuit by operating a commercial APD cooled to -20{\deg}C with a deadtime of 35ns while maintaining the after-pulsing probability at close to 3%. We also showcase its versatility by operating custom-fabricated chip-scale APDs, which paves the way for automated wafer-scale characterization.