High-efficiency photon-counting fluorometer with a channel width of 5.0 ps

We construct a photon-counting, fluorescence lifetime measurement system with a channel width of 5.0 ps. This is a modified version of our previous fluorometer based on a simultaneous detection method of photoelectron pulse trains after pulsed excitation (Iwata in Meas Sci Technol 28:075501, 2017), which can accept multiple photons during a one period of the excitation for building a histogram. Although the resolution time is 2.0 ns as before, the channel width of 5.0 ps is of the same order as that of time-correlated single-photon counting, which is achieved by delaying the trigger timing for the fluorometer by a step to that of the excitation. This results in an increase in the precision for the lifetime estimation. Although the measurement time increases with increasing the number of delay steps, it is still rather shortened owing to the high signal-gathering and histogram-building efficiencies.