Characterisation of a Low-Noise Tuneable Silicon Single-Photon Avalanche Diode

Silicon single-photon avalanche diodes (Si-SPADs) are widely used in lightwave applications such as quantum communication, medical imaging, time-of-flight systems and quantum optical metrology, due to their sensitivity, accuracy, compactness and cost-effectiveness. The most important performance metric depends on its intended application. Each metric has a dependence on operating parameters such as bias voltage and operating temperature. Some metrics, e.g. detection efficiency and timing precision, exhibit performance trade-offs with noise. However, plug-and-play Si-SPADs typically have fixed bias voltage and operating temperature, which significantly limits user control, adaptability, and performance. In this study, a recently developed commercially available free-space Si-SPAD with adjustable bias voltage, temperature control, an integrated frequency counter and a large sensing area was evaluated. Key performance metrics were traceably measured as functions of bias voltage and temperature, including dark count rate, dead time, timing precision, afterpulse probability and photon detection efficiency at 852 nm. Results are benchmarked against existing reports of other commercially available Si-SPAD detectors. Notable strengths include low dark count rates (4 to 10 s-1), a large sensing area (diameter = 500 μm), and high timing precision (163 to 212 ps), whilst maintaining a detection efficiency greater than 40%. These characteristics make the detector a strong candidate for deployment across a range of applications, particularly those operating outside of lab conditions where operational flexibility is essential.