Simultaneous detection of CH 4 and CO 2 through dual modulation off-axis integrated cavity output spectroscopy

• Published in: Chinese physics B 2023-11, Vol.32 (10), p.104209
• Main Authors: Liu 刘, Yi-Xuan 艺璇, Wang 王, Zhou-Bing 周兵, Wei 韦, Xin-Xin 欣欣, Wang 王, Jing-Jing 静静, Meng 孟, Xin 鑫, Mao 毛, Gui-Lin 桂林
• Format: Article
• Language: English
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/acdac1

This study established a novel method for the simultaneous detection of two-component gases. Radio frequency (RF) white noise disturbance laser current and wavelength modulation were simultaneously used to improve the off-axis integrated cavity output spectroscopy technique, and a high-precision dual modulation OA-ICOS (RF-WM-OA-ICOS) system was established. The two laser beams were coupled into one laser beam that was applied incident to the cavity of RF-WM-OA-ICOS system. The second harmonic signals of CH 4 and CO 2 gas simultaneously appeared in the rising or falling edge of a triangular wave. This method was used to measure CH 4 and CO 2 with different concentrations. The results indicated that the proposed system has high stability and can accurately and simultaneously measure the concentrations of CH 4 and CO 2 , with an optimal integration time of 220 s. The minimum detection limit was 10 ppb for CH 4 and 1.5 ppm for CO 2 . The corresponding noise equivalent absorption sensitivity values were calculated as 2.67 × 10 −13 cm −1 ⋅Hz −1/2 and 5.18 × 10 −11 cm −1 ⋅Hz −1/2 , respectively. The proposed dual-component gas simultaneous detection method can also be used for high-precision simultaneous detection of other gases. Therefore, this study may serve as a reference for developing portable multicomponent gas analyzers.