Gong Miaoxin, Kim Haisol, Larsson Jim, Methling Torsten, Aldén Marcus, Kristensson Elias, Brackmann Christian, Eschrich Tina, Jäger Matthias, Kiefer Wolfgang, Ehn Andreas
Opt Express. 2021 Mar 1;29(5):7232-7246. doi: 10.1364/OE.410517.
Stray light is a known strong interference in spectroscopic measurements. Photons from high-intensity signals that are scattered inside the spectrometer, or photons that enter the detector through unintended ways, will be added to the spectrum as an interference signal. A general experimental solution to this problem is presented here by introducing a customized fiber for signal collection. The fiber-mount to the spectrometer consists of a periodically arranged fiber array that, combined with lock-in analysis of the data, is capable of suppressing stray light for improved spectroscopy. The method, which is referred to as fiber-based periodic shadowing, was applied to Raman spectroscopy in combustion. The fiber-based stray-light suppression method is implemented in an experimental setup with a high-power high-repetition-rate laser system used for Raman measurements in different room-temperature gas mixtures and a premixed flame. It is shown that the stray-light level is reduced by up to a factor of 80. Weak spectral lines can be distinguished, and therefore better molecular species identification, as well as concentration and temperature evaluation, were performed. The results show that the method is feasible and efficient in practical use and that it can be employed as a general tool for improving spectroscopic accuracy.
杂散光在光谱测量中是一种已知的强干扰。来自在光谱仪内部散射的高强度信号的光子，或者通过非预期方式进入探测器的光子，会作为干扰信号被添加到光谱中。本文通过引入定制的信号收集光纤，提出了一种针对该问题的通用实验解决方案。安装到光谱仪上的光纤由周期性排列的光纤阵列组成，该阵列与数据的锁相分析相结合，能够抑制杂散光以改善光谱分析。这种方法被称为基于光纤的周期性遮蔽，已应用于燃烧过程中的拉曼光谱分析。基于光纤的杂散光抑制方法在一个实验装置中得以实现，该装置配备了高功率高重复率激光系统，用于在不同室温气体混合物和预混火焰中进行拉曼测量。结果表明，杂散光水平降低了多达80倍。可以分辨出微弱的光谱线，因此能够进行更好的分子种类识别以及浓度和温度评估。结果表明，该方法在实际应用中是可行且高效的，并且可以用作提高光谱精度的通用工具。
