time-correlated single-photon counting (TCSPC)

Time-correlated single-photon counting (TCSPC) is a precise technique used to measure the time it takes for a tiny pulse of light (a photon) to travel from a source to a detector. When a light source emits a photon, the system records the exact moment it occurs. By repeating this process many times and measuring the arrival times, TCSPC builds a detailed histogram that reveals how the light behaves over time, such as fluorescence decay. This method enables highly accurate analysis of fast processes in materials, biology, and physics, with timing resolutions often in the picoseconds (trillionths of a second).