Sub-ppb detection of nitrogen dioxide with an external cavity quantum cascade laser

Rafal Lewicki; Kun Liu; Timothy Day; Frank K. Tittel

doi:10.1117/12.908402

20 January 2012 Sub-ppb detection of nitrogen dioxide with an external cavity quantum cascade laser

Rafal Lewicki, Kun Liu, Timothy Day, Frank K. Tittel

Proceedings Volume 8268, Quantum Sensing and Nanophotonic Devices IX; 82682H (2012) https://doi.org/10.1117/12.908402
Event: SPIE OPTO, 2012, San Francisco, California, United States

Abstract

Ultra-sensitive detection of nitrogen dioxide (NO₂) in the ν3 fundamental band of NO₂ using Faraday Rotation Spectroscopy (FRS) based optical sensor platform is reported. The FRS technique is well suited for selective trace gas measurements of paramagnetic species including the prominent air pollutants such as NO or NO₂. In this paper a widely tunable external cavity quantum cascade laser (EC-QCL) is employed as an excitation source. The available EC-QCL mode-hop free tuning range between 1600 cm^-1 and 1650 cm^-1 allows to access the optimum for FRS technique 4₄₁<-4₄₀ Q-branch NO₂ transition at 1613.2 cm^-1 with an optical power of ~135 mW. In order to improve detection sensitivity and reduce size of the sensor platform, a custom made 22.47 cm long Herriott multipass gas cell (MPC) with a total effective optical path of 10.1 m was implemented. For a MPC configured NO₂ FRS sensor operating in line-scanning mode a minimum detection limit of 1.6 ppbv (1σ) and 0.15 ppb (1σ) is achieved for a 1 sec and 100 sec averaging time, respectively. Preliminary results for long term measurements of atmospheric NO₂ for the FRS sensor operating at an optimal pressure of 30 Torr and magnetic field of 200 Gaussrms were demonstrated.

Citation Download Citation

Rafal Lewicki, Kun Liu, Timothy Day, and Frank K. Tittel "Sub-ppb detection of nitrogen dioxide with an external cavity quantum cascade laser", Proc. SPIE 8268, Quantum Sensing and Nanophotonic Devices IX, 82682H (20 January 2012); https://doi.org/10.1117/12.908402

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