High count rate InGaAs/InP SPAD system with balanced SPAD-dummy approach running up to 1.4 GHz

The capability to achieve high count rates has become an imperative in the most areas where near-infrared single-photon counters are required to detect photons up to 1.7 μm. Hence, afterpulsing mitigation is a dominant theme in recent works concerning systems based on InGaAs/InP SPADs. Given the challenges inherent in reducing the density of defects that give rise to the carrier trapping events causing afterpulsing, the only viable approach is to reduce the potential number of carriers that can be trapped by limiting the charge flow per avalanche event. In this paper we present a sine-wave gating system based on the balanced detector configuration. The gate frequency is programmable in a wide range (1.0 – 1.6 GHz) for allowing synchronization with an external laser system and for exploring the best trade-off between afterpulsing and photon detection efficiency. The long-term stability can be achieved with a stable cancelation of the gate feedthrough. In this work this is guaranteed by a feedback loop that continuously monitors the residual output power at the gate frequency and adjusts the amplitude and phase of the two sinusoids fed to the SPAD-dummy couple.