High Accurate Range Finding With Spads At 1064nm

Single photon avalanche diodes (SPADs), operated in Geiger mode, provide highest detection efficiency for time of flight measurements in the single photon regime. However, the risetime of the output signal shows time delays with changing number of generated photoelectrons. Therefore the measured time of arrival shows some drift with changing input light levels. Based on the continuity equations and the intrinsic resistance of SPADs, a simple model of the avalanche breakthrough was developed to analyze this behavior. By applying a suitable external gating circuit, e. g. implementing a decoupling resistor between the diode and the gating capacitor, this simulation shows a slight dependency of the diodes peak output current on the number of generated photoelectrons. Experimental observations performed with a passive quenching circuit and an InGaAs/InP-SPAD showed good agreement with the simulation. In time of flight measurements, e. g. in satellite laser ranging, this behavior can be used for compensating intensity dependent delays during the detection process.