Editing Single-photon avalanche diode (section)

=== Photon timing and jitter ===
The leading edge of a SPAD's avalanche breakdown is particularly useful for timing the arrival of photons. This method is useful for 3D imaging, LIDAR and is used heavily in physical measurements relying on [[time-correlated single photon counting]] (TCSPC). However, to enable such functionality dedicated circuits such as time-to-digital converters (TDCs) and time-to-analogue (TAC) circuits are required. The measurement of a photon's arrival is complicated by two general processes. The first is the statistical fluctuation in the arrival time of the photon itself, which is a fundamental property of light. The second is the statistical variation in the detection mechanism within the SPAD due to a) depth of photon absorption, b) diffusion time to the active p-n junction, c) the build up statistics of the avalanche and d) the jitter of the detection and timing circuitry.