Realizing a robust, reconfigurable active quenching design for multiple architectures of single-photon avalanche detectors

TL;DR

This paper introduces a reconfigurable, robust active quenching circuit for single-photon detectors using a System-on-Chip that allows dynamic parameter adjustment, field calibration, and is suitable for space applications.

Contribution

A novel hybrid SoC-based active quenching design that is reconfigurable, field-adjustable, and rugged for space and quantum communication applications.

Findings

Achieved a 35ns deadtime with 3% after-pulsing probability.

Demonstrated compatibility with commercial and custom APDs.

Enabled remote control and re-calibration in the field.

Abstract

Most active quench circuits used for single-photon avalanche detectors 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 configuration capabilities to vary the quench and reset parameters dynamically over a large range, thus allowing our circuit to operate with a wide variety of APDs without having to re-design the system. The microcontroller enables the remote adjustment of control parameters and re-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 characterize our circuit with a commercial APD cooled to 253K, and obtain a deadtime of 35ns while maintaining the after-pulsing probability at close to 3%. We also demonstrate versatility of the circuit by directly testing custom fabricated chip-scale APDs, which paves the way for automated wafer-scale testing and characterization.