Fast fully integrated active quenching circuit for single photon counting up to 160 Mcounts/s

Single-photon detection capabilities of Single Photon Avalanche Diodes (SPADs), in laser ranging, enable the measurement of significantly long ranges, the minimization of the optical power of the laser source and the implementation of high frame rate 3D imaging systems, thanks to the possibility of using an array. However, some disadvantages intrinsically affect the Geiger mode operation: above all, each time a photon is detected, the SPAD cannot record another photon during the so-called dead time. The minimization of this dead time is of paramount importance in many cases. For example, in airborne LIDAR altimeters that scan the terrain topography through a semiporous obscuration (e.g. tree canopies, clouds, ground fog, etc.), the first photons that are reflected can mask the photons actually scattered by the terrain: in this scenario, a dead time in the nanosecond range allows the record of photons reflected by surfaces having a distance of few meters. Moreover, a fast recovery of the detector is crucial in presence of a strong background when the LIDAR receiver can fall into paralyzation due to the high rate of photon detections. Here, we present a new Active Quenching Circuit (AQC) able to operate external high-performance custom technology SPAD detectors at extremely high rates. In particular, the circuit can drive a thin custom-technology SPAD with a dead time as low as 6.2ns, corresponding to a maximum photon count rate of more than 160 Mcps, and a RED-Enhanced SPAD up to 100Mcps.