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Open AccessArticle

Quantitative Evaluation of Broadband Photoacoustic Spectroscopy in the Infrared with an Optical Parametric Oscillator

by 1,2,‡, 1, 1,2 and 2,3,*,†,‡
1
Hochschule für Angewandte Wissenschaften Hamburg, Fakultät Technik und Informatik, Department Maschinenbau und Produktion, Berliner Tor 21, 20099 Hamburg, Germany
2
School of Engineering and Computing, University of the West of Scotland, High Street, Paisley PA1 2BE, UK
3
Scottish University Physics Alliance (SUPA), University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
*
Author to whom correspondence should be addressed.
Current address: Extreme Light Infrastructure (ELI-NP) & IFIN-HH, Horia Hulubei National Institute of Physics and Nuclear Engineering, Str. Reactorului no.30, P.O. box MG-6, Bucharest, Măgurele, Romania.
These authors contributed equally to this work.
Sensors 2018, 18(11), 3971; https://doi.org/10.3390/s18113971
Received: 5 September 2018 / Revised: 6 November 2018 / Accepted: 7 November 2018 / Published: 15 November 2018
(This article belongs to the Section Physical Sensors)
We evaluate the spectral resolution and the detection thresholds achievable for a photoacoustic spectroscopy (PAS) system in the broadband infrared wavelength region 3270 n m λ 3530 n m driven by a continuous wave optical parametric oscillator (OPO) with P ¯ 1.26 W . The absorption spectra, I PAS ( λ i ) , for diluted propane, ethane and methane test gases at low concentrations ( c 100 ppm ) were measured for ∼1350 discrete wavelengths λ i . The I PAS ( λ i ) spectra were then compared to the high resolution cross section data, σ FTIR , obtained by Fourier Transform Infrared Spectroscopy published in the HITRAN database. Deviations of 7.1(6)% for propane, 8.7(11)% for ethane and 15.0(14)% for methane with regard to the average uncertainty between I PAS ( λ i ) and the expected reference values based on σ FTIR were recorded. The characteristic absorption wavelengths λ res can be resolved with an average resolution of δ λ res 0.08 nm . Detection limits range between 7.1 ppb (ethane) to 13.6 ppb (methane). In an additional step, EUREQA, an artificial intelligence (AI) program, was successfully applied to deconvolute simulated PAS spectra of mixed gas samples at low limits of detection. The results justify a further development of PAS technology to support e.g., biomedical research. View Full-Text
Keywords: photoacoustic spectroscopy; PAS; hydrocarbons; optical-parametric oscillator; OPO; gas sampling; spectral deconvolution; EUREQA photoacoustic spectroscopy; PAS; hydrocarbons; optical-parametric oscillator; OPO; gas sampling; spectral deconvolution; EUREQA
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MDPI and ACS Style

Bruhns, H.; Wolff, M.; Saalberg, Y.; Spohr, K.M. Quantitative Evaluation of Broadband Photoacoustic Spectroscopy in the Infrared with an Optical Parametric Oscillator. Sensors 2018, 18, 3971.

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