Monolithic Multi-Detector System for Single-Photon Timing Applications

Time Correlated Single Photon Counting (TCSPC) has gained wide acceptance in recent years and is currently exploited in new analytical and diagnostic techniques, such as Fluorescence Lifetime Imaging (FLIM) and Optical Tomography. Applications in multidimensional measurements require arrays of single-photon detectors with high photon detection efficiency, low dark counting rate, low optical and electrical crosstalk and high timing performance. Silicon Single Photon Avalanche Diodes (SPADs) are today a solid-state alternative to photomultiplier tubes and can be integrated for producing at low cost monolithic arrays with low power dissipation and high detection efficiency. However, for attaining a precise photon timing (time jitter <100 ps) contributions to the time jitter due to the propagation of the avalanche over the pixel area must be avoided by sensing truly the onset of the avalanche (i.e. the current at very low level 10-20 µA). The development in the detector technology of a new front-end circuitry integrated in the detector chip has made possible this approach, which was otherwise inhibited by the cross-talk between adjacent channels in external electronic circuitry.