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Time-correlated single-photon lidar is a technology that can provide high resolution lidar measurements, with low laser power, providing many applications in defence and security. One problem with the InGaAs/InP single photon avalanche detectors (SPAD), which are sensitive around 1.55 μm, is that they suffer from afterpulsing from trapped carriers. This is usually solved by having a hold-off time before reapplying the voltage to the detector, after a detection, to let the trapped carriers dissipate. For InGaAs SPAD this hold-off time, during which the detector is insensitive to photons, needs to be several microseconds to avoid runaway afterpulsing and tens of microseconds to get low afterpulsing.
This paper describes a model to calculate the received number of laser photons in lidar experiments, under the influence of detector dark counts, ambient background, afterpulsing and hold-off time. By using characterization data of photon detection efficiency, dark count rate and afterpulsing, for different detector settings, graphs of optimum operation points for different signal and background levels are simulated. Some comparisons to experimental data are performed.
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