The time-resolution can be obtained in a number of ways, depending on the required sensitivity and time regions. Edinburgh Instruments employs the technique called Time-Correlated Single Photon Counting (TCSPC), for Time-Resolved Fluorescence, which is used for the acquisition of single photons and allows for time resolutions in the range of picoseconds (ps) to nanoseconds (ns).

This technique is a digital counting technique, counting photons that are time-correlated in relation to a short excitation light pulse. In TCSPC the sample is repetitively excited using a pulsed light source with a high repetition rate. During the measurement a probability histogram builds, which relates the time between an excitation pulse (START) and the observation of the first fluorescence photon (STOP). The fact that the time at which a fluorescence photon is incident on the detector can be defined with picosecond resolution is critical to the operation and precision of TCSPC. To study lifetime decays slower than this (ns to seconds time range) please see Phosphorescence Lifetime.

To find out more about what TCSPC is and why we use TCSPC, please see the technical notes provided in the resources section.