基于SiPM和TCMPC的时间分辨拉曼散射测量技术研究

报道了一种基于硅光电信增管(SiPM)的时间相关多光子计数(TCMPC)技术并将其应用于时间分辨拉曼散射测量。相比于常规基于光电倍增管(PMT)或单光子雪崩二极管(SPAD)的时间相关单光子(TCSPC)技术，由于SiPM可以分辨信号脉冲的具体光子数，基于SiPM的TCMPC技术消除了信号脉冲包含的光子数必须小于等于1的限制，光子计数效率提高了10倍以上，大大节省了测量时间。此外，多光子测量比单光子测量能够得到更好的时间分辨率，时间分辨拉曼散射系统的仪器响应函数(IRF)从单光子81.4 ps缩短至双光子59.7 ps，因而可以用更窄的时间门限抑制荧光本底等噪声对拉曼散射测量的影响。使用TCMPC技术测量CCl₄在0.5和1.5 p.e.两个不同光子数阈值的拉曼峰的峰本比，后者较高的光子数阈值能进一步降低SiPM暗计数噪声的影响，增加了拉曼信号测量的信噪比，测量得到的CCl₄ 459 cm-1拉曼峰的峰本比是前者的6.4倍。将所述新的拉曼散射测量技术与基于PMT和锁相放大器(LIA)的传统拉曼散射测量技术进行了比较研究，前者由于可以使用仅有数十皮秒的测量门限，可以有效抑制荧光、环境杂散光和SiPM暗计数等噪声的影响，所得光谱具有更好的峰本比，测得CCl₄的459 cm-1拉曼峰和Si的一阶拉曼峰的峰本比分别是后者的3.9倍和5.5倍。

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.