Time-Resolved Raman Scattering Measurement Based on SiPM and TCMPC Method

This paper reports a time-correlated multi-photon counting (TCMPC) technique based on SiPM and its application to time-resolved Raman scattering measurements. Compared with conventional time-correlated single photon counting (TCSPC) technique by using photomultiplier (PMT) or single photon avalanche diode (SPAD) as photon detector, SiPM can distinguish the specific photon-number of the signal pulse, the TCMPC technique based on SiPM eliminates the limitation of the number of photons contained in signal pulse, which must be less than or equal to 1, leading to an increment of the photon counting efficiency by more than 10 times, and greatly reduces the measurement time. In addition, the instrument response function (IRF) of the time-resolved Raman scattering system is enhanced from 81. 4 ps for single-photon to 59.7 ps for two-photon detection due to higher time resolution for multi-photon counting than single-photon counting measurement. As a result, it is possible to use a narrower measuring time span to suppress the fluorescence background, a kind of noise that usually occurs in conventional Raman spectroscopy. The TCMPC technique is used to measure the peak-to-background ratio of Raman spectroscopy of CCl4 with different photon numbers of 0. 5 p. e. and 1. 5 p. e., because the later has a higher photo-electron threshold number that can further reduce the effect of SiPM dark counting and increase the signal-to-noise ratio of Raman spectroscopy, the measured peak to-background ratio of CCl4 459 cm(-1) Raman peak has increased 6. 4 times compared with the former. The TCMPC based on Raman scattering measurement technique is compared with the conventional one based on photomultiplier tube (PMT) and lock-in amplifier (LIA). As the timing gate of only several tens of picoseconds is utilized, effective suppression of fluorescence, ambient stray light, dark counting of SiPM and other noise effects have been demonstrated, leading to a better peak-to-background ratio for Raman spectroscopy. The peak-to-background ratios of CCl4 459 cm(-1) Raman peak and Si 1st Raman peak, measured by the TCMPC based on Raman spectrometer are 3. 9 times and 5. 5 times as high as the values obtained by the one based on PMT and LIA, respectively.