Detection rate dependence of the inherent detection efficiency in single-photon detectors based on avalanche diodes

Single-photon detectors are a pivotal component in photonic quantum technologies. A precise and comprehensive calibration of the inherent detection efficiency is of utmost importance to ensure the proper evaluation of the performance in view of the specific technological application of interest, such as the protection against security breaches in quantum cryptographic solutions. Here we report on a systematic study and comprehensive analysis of the estimation of the inherent detection efficiency of two commercial single-photon detectors based on single-photon avalanche diodes for various mean photon numbers and at high laser pulse repetition rates using different techniques. We observe an unexpected and significant drop in the inherent detection efficiency at detection rates of 10% and higher relative to the maximum detection rate. It is demonstrated that for data analysis a statistical model for the detection rate conveniently can be used if no time-stamped data are available. We conclude that the full characterization of single-photon detectors used in critical applications should include the sensitivity of their inherent detection efficiency to high event rates.