Determine optimal single-photon detector (APD vs. SiPM) for TD‑fNIRS

Determine, through detailed experimental characterization, whether an actively-quenched avalanche photodiode or a silicon photomultiplier is more suitable as the single-photon detector in a high-count-rate time-domain functional near-infrared spectroscopy system for visual image reconstruction, given the system requirements and constraints described by the authors.

Background

The paper develops a low-cost time-domain fNIRS prototype and evaluates two detector options: an actively quenched avalanche photodiode (APD) and a silicon photomultiplier (SiPM). Both detectors were demonstrated to detect single photons and to meet the required dead-time constraints for building distribution-of-time-of-flights histograms.

However, the authors note that a decisive choice between APD and SiPM cannot be made without further characterization, due to trade-offs in dark counts, coupling practicality, and unmeasured timing jitter. This leaves the detector selection unresolved pending systematic comparison under realistic operating conditions.