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Proceedings Paper

Open-path remote sensing for multi-species gas detection using a broadband optical parametric oscillator
Author(s): Oguzhan Kara; Frazer Sweeney; Marius Rutkauskas; Carl Farrell; Christopher G. Leburn; Derryck T. Reid
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Paper Abstract

We demonstrate path-integrated simultaneous concentration measurements of water, methane and ethane, measuring spectra across the 3.1–3.5-μm range using 0.05 cm-1 resolution Fourier-transform spectroscopy in-line with an ultrafast optical parametric oscillator and a simple, non-compliant target. Illumination spectra were extracted from a fitting procedure which simultaneously minimized the rms error between the experimental spectrum and a synthetic spectrum calculated from the envelope and a fitted mixture of PNNL or HITRAN absorbance data for water, methane and ethane. Simultaneous methane, ethane and water measurement at 30-m range were initially performed. Indoor measurements launched light from the OPO through a 20-cm-long gas cell containing a 1.5±0.15% ethane-in-air mixture. Light was reflected from a rough Al-foil target. Best-fit concentrations were determined to be 1.15% (water), 1860 ppb (methane) and 1.37 % (ethane). The methane background value is consistent with reported ambient levels. Respective water and ethane values were consistent with the ambient relative humidity. The second experiment demonstrated real-time methane emission measurement at 70-m range. A 2% methane:air mix was released for 100 seconds at a rate of 103 μgs-1 at a distance of 65 m from the OPO. The signal was recorded from a simple target of rough aluminum foil situated 70 m from the OPO, with the beam passing near the emission point. This work demonstrates our ability to extract concentration data from a single spectrum with no need for averaging, which provides a real-time and quantitative monitoring capability.

Paper Details

Date Published: 2 March 2020
PDF: 7 pages
Proc. SPIE 11265, Real-time Measurements, Rogue Phenomena, and Single-Shot Applications V, 112650Q (2 March 2020); doi: 10.1117/12.2551702
Show Author Affiliations
Oguzhan Kara, Heriot-Watt Univ. (United Kingdom)
Frazer Sweeney, Heriot-Watt Univ. (United Kingdom)
Marius Rutkauskas, Heriot-Watt Univ. (United Kingdom)
Carl Farrell, Chromacity Ltd. (United Kingdom)
Christopher G. Leburn, Chromacity Ltd. (United Kingdom)
Derryck T. Reid, Heriot-Watt Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 11265:
Real-time Measurements, Rogue Phenomena, and Single-Shot Applications V
Daniel R. Solli; Georg Herink; Serge Bielawski, Editor(s)

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