Off-axis cavity-enhanced absorption spectroscopy of 14NH3 in air using a gain-switched frequency comb at 1.514 μm

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Chandran, Satheesh
Ruth, Albert A.
Martin, Eamonn P.
Alexander, Justin K.
Peters, Frank H.
Anandarajah, Prince M.
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A custom-designed gain-switched frequency comb (GSFC) source was passively coupled to a medium finesse (F ≈ 522) cavity in off-axis configuration for the detection of ammonia (14NH3) in static dry air. The absorption of ammonia was detected in the near infrared spectral region between 6604 and 6607 cm−1 using a Fourier transform detection scheme. More than 30 lines of the GSFC output (free spectral range 2.5 GHz) overlapped with the strongest ro-vibrational ammonia absorption features in that spectral region. With the cavity in off-axis configuration, an NH3 detection limit of ∼3.7 ppmv in 20 s was accomplished in a laboratory environment. The experimental performance of the prototype spectrometer was characterized; advantages, drawbacks and the potential for future applications are discussed
Cavity-enhanced absorption spectroscopy , Off-axis alignment , Frequency comb , Gain switching , Near infrared (IR) range , Fourier transform spectroscopy , NH3 sensing , Ammonia detection
Chandran, S., Ruth, A. A., Martin, E. P., Alexander, J. K., Peters, F. H. and Anandarajah, P. M. (2019) 'Off-Axis Cavity-Enhanced Absorption Spectroscopy of 14NH3 in Air Using a Gain-Switched Frequency Comb at 1.514 μm', Sensors, 19 (23), 5217 (15 pp). doi: 10.3390/s19235217
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