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Article

Off-Axis Cavity-Enhanced Absorption Spectroscopy of 14NH3 in Air Using a Gain-Switched Frequency Comb at 1.514 μm

1
Physics Department & Environmental Research Institute, University College Cork, Cork, Ireland
2
School of Electronic Engineering, Dublin City University, Glasnevin, Dublin 9 D09 W6Y4, Ireland
3
Physics Department & Tyndall National Institute, University College Cork, Cork, Ireland
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(23), 5217; https://doi.org/10.3390/s19235217
Received: 23 October 2019 / Revised: 21 November 2019 / Accepted: 26 November 2019 / Published: 28 November 2019
(This article belongs to the Section Optical Sensors)
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. View Full-Text
Keywords: cavity-enhanced absorption spectroscopy; off-axis alignment; frequency comb; gain switching; near infrared (IR) range; Fourier transform spectroscopy; NH3 sensing; ammonia detection cavity-enhanced absorption spectroscopy; off-axis alignment; frequency comb; gain switching; near infrared (IR) range; Fourier transform spectroscopy; NH3 sensing; ammonia detection
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MDPI and ACS Style

Chandran, S.; Ruth, A.A.; Martin, E.P.; Alexander, J.K.; Peters, F.H.; Anandarajah, P.M. Off-Axis Cavity-Enhanced Absorption Spectroscopy of 14NH3 in Air Using a Gain-Switched Frequency Comb at 1.514 μm. Sensors 2019, 19, 5217. https://doi.org/10.3390/s19235217

AMA Style

Chandran S, Ruth AA, Martin EP, Alexander JK, Peters FH, Anandarajah PM. Off-Axis Cavity-Enhanced Absorption Spectroscopy of 14NH3 in Air Using a Gain-Switched Frequency Comb at 1.514 μm. Sensors. 2019; 19(23):5217. https://doi.org/10.3390/s19235217

Chicago/Turabian Style

Chandran, Satheesh, Albert A. Ruth, Eamonn P. Martin, Justin K. Alexander, Frank H. Peters, and Prince M. Anandarajah. 2019. "Off-Axis Cavity-Enhanced Absorption Spectroscopy of 14NH3 in Air Using a Gain-Switched Frequency Comb at 1.514 μm" Sensors 19, no. 23: 5217. https://doi.org/10.3390/s19235217

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