Experimental-based comparison between off-axis integrated cavity output spectroscopy and multipass-assisted wavelength modulation spectroscopy at 7.7 mu m
| Autor: | Simona M. Cristescu, Julien Mandon, Faisal Nadeem, Frans J. M. Harren, Amir Khodabakhsh |
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| Rok vydání: | 2019 |
| Předmět: |
Detection limit
Materials science Absorption spectroscopy business.industry Linearity Atomic and Molecular Physics and Optics Spectral line Electronic Optical and Magnetic Materials law.invention Trace gas Optics law Continuous wave Molecular and Laser Physics Electrical and Electronic Engineering business Quantum cascade laser Spectroscopy |
| Zdroj: | Osa Continuum, 2, 2667-2682 Osa Continuum, 2, 9, pp. 2667-2682 |
| ISSN: | 2578-7519 |
| Popis: | A mid-infrared trace gas detection system based on off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and sensitive detection of N2O in combination with a continuous wave external-cavity quantum cascade laser (EC-QCL) working around 7.7 µm. A 13-times improvement in signal-to-noise ratio is achieved using a re-injection mirror and a minimum detection limit of 70 ppbv in less than 10 s averaging time is achieved, which yields a noise-equivalent absorption sensitivity (NEAS) of 6×10−9 cm−1 Hz−1/2. For comparison, a compact multipass cell is deployed to measure the same absorption line of N2O using wavelength modulation spectroscopy with second harmonic detection (WMS-2f). An enhancement factor of 20 in comparison to direct absorption spectroscopy (DAS) is achieved, yielding a minimum detection limit of 15 ppbv in less than 10 s averaging and a NEAS of 1×10−9 cm−1 Hz−1/2. A comprehensive comparison between the two systems is carried out in terms of residual amplitude noise (RAM), linearity, long-term stability, detection limit, spectral fitting, reproducibility, and background variations. The proposed sensor based on OA-ICOS is potentially advantageous for trace gas sensing in outdoor applications and harsh environments due to its robustness and flexibility of alignment. |
| Databáze: | OpenAIRE |
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