Ultrafast laser spectroscopy

Under time-correlated single photon counting (English time- correlated single photon counting, TCSPC ) is a technique for measuring in time of rapidly changing ( picosecond ) light intensities. Main application is the measurement of the fluorescence lifetime and based on it techniques such as fluorescence lifetime microscopy (English fluorescence lifetime imaging microscopy, FLIM ). But the analysis of the temporal behavior of pulsed or modulated light sources, making it possible to the characterization of circulating electron bunches in storage rings of synchrotrons basis of the votes synchrotron radiation.

For the measurement of fluorescence lifetime ( such as laser or flash lamp) are stimulated to be examined by means of a pulsed light source fluorophores. The time measurement is started by the excitation pulse and the emitted to the ground state in the transition from the excited state photon stops the measurement. The measurement is repeated many times and each time correlated photons ( with respect to the excitation pulse) are sorted according to their measured time in a so-called TCSPC histogram. This typically has a temporal resolution channel or class width of about 1 to 50 ps, and outputs the exponential decay of the fluorescence intensity after excitation again.

The fluorescence lifetime can be determined depending on the measurement technique used in the time domain (german time domain ) or the frequency domain ( engl. frequency domain ), the time-correlated single photon counting is the most commonly used method in the time domain.