Photonics Laboratory, Physics Unit, Tampere University, FI-33014 Tampere, Finland.
Gasera Ltd., Lemminkäisenkatu 59, FI-20520 Turku, Finland.
Phys Chem Chem Phys. 2022 Aug 17;24(32):19481-19487. doi: 10.1039/d2cp01731h.
We report multipass broadband photoacoustic spectroscopy of trace gases in the mid-infrared. The measurement principle of the sensor relies on supercontinuum-based Fourier transform photoacoustic spectroscopy (FT-PAS), in which a scanning interferometer modulates the intensity of a mid-infrared supercontinuum light source and a cantilever microphone is employed for sensitive photoacoustic detection. With a custom-built external Herriott cell, the supercontinuum beam propagates ten times through a miniature and acoustically non-resonant gas cell. The performance of the FT-PAS system is demonstrated by measuring the fundamental C-H stretch bands of various hydrocarbons. A noise equivalent detection limit of 11 ppb is obtained for methane (40 s averaging time, 15 μW cm incident power spectral density, 4 cm resolution), which is an improvement by a factor of 12 compared to the best previous FT-PAS systems. High linearity and good stability of the sensor provide reliable identification of individual species from a gas mixture with strong spectral overlap, laying the foundation for sensitive and selective multi-species detection in small sample volumes.
我们报告了中红外痕量气体的多通宽带光声光谱。传感器的测量原理依赖于基于超连续的傅里叶变换光声光谱（FT-PAS），其中扫描干涉仪调制中红外超连续光源的强度，悬臂式麦克风用于灵敏的光声检测。通过定制的外部 Herriott 池，超连续光束在微型非声学共振气体池中传播十次。通过测量各种碳氢化合物的基本 C-H 伸缩带，展示了 FT-PAS 系统的性能。对于甲烷（40 s 平均时间、15 μW cm 入射功率谱密度、4 cm 分辨率），获得了 11 ppb 的噪声等效检测限，与之前最好的 FT-PAS 系统相比提高了 12 倍。传感器的高线性度和良好的稳定性为从具有强光谱重叠的混合气体中可靠地识别单个物种提供了基础，为在小样本体积中进行灵敏和选择性多物种检测奠定了基础。
