LAUSR

High afterpulse probability and the consequent long dead time of free-running InGaAs(P) single-photon detectors have long been the limiting factors to their practical applications. Here we present a free-running InGaAsP single-photon detector for 1.06 μm wavelength with ultra-low dead time and afterpulse probability. With the optimized active-quenching circuit and packaging, the avalanche pulse discrimination level is down to 2.4 mV, and the full-width at half-maximum of the avalanche pulse is as short as 500 ps, which greatly lessens afterpulsing effects. As a result, the dead time of the detector is as low as 35 ns, comparable to free-running silicon detectors, with a low afterpulse probability of 11.6% at 10% detection efficiency, 242 K. The proposed detector provides a high-performance, small-sized, low-power approach to single-photon detection for practical applications such as light detection and ranging and free-space quantum key distribution systems.