Zorin Ivan, Kilgus Jakob, Duswald Kristina, Lendl Bernhard, Heise Bettina, Brandstetter Markus
Research Center for Non-Destructive Testing, Linz, Austria.
Institute for Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
Appl Spectrosc. 2020 Apr;74(4):485-493. doi: 10.1177/0003702819893364. Epub 2020 Feb 25.
Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 µm path length) and compared with the conventional FT-IR (130 µm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.
几十年来，傅里叶变换红外（FT-IR）光谱仪一直是中红外（mid-IR）光谱领域的主导技术。工作在中红外光谱区域的超连续谱激光源，由于其具有高亮度、宽带光谱覆盖和增强稳定性等独特特性，现在为丰富FT-IR光谱领域提供了潜力。在我们的研究中，我们引入这种先进的光源来替代传统的热辐射源。此外，还提出并详细考虑了一种将脉冲中红外超连续谱源高效耦合到FT-IR光谱仪的方法。实验部分致力于所应用的超连续谱激光的逐脉冲能量波动、系统性能以及噪声和长期稳定性。使用配备热辐射源的传统FT-IR仪器进行的对比测量表明，基于超连续谱的系统可以实现类似的噪声水平。在液体流通池（光程长度为500 µm）中对一系列甲醛水溶液浓度进行了基于超连续谱的FT-IR光谱仪的分析性能测试，并与传统FT-IR（光程长度为130 µm）进行了比较。结果表明，由于激光的高亮度使得光程长度得以延长，检测限提高了四倍。总之，配备新型宽带中红外超连续谱激光的FT-IR光谱仪可能优于传统系统，提供卓越的性能，例如以前无法达到的相互作用光程长度，同时保持从高度稳定的热辐射源已知的低噪声水平。
