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

Abstract

We evaluate the spectral resolution and the detection thresholds achievable for a photoacoustic spectroscopy (PAS) system in the broadband infrared wavelength region 32700.166667emnm≲λ≲35300.166667emnm driven by a continuous wave optical parametric oscillator (OPO) with P¯-0.166667em≈-0.166667em1.260.166667emnormalW. The absorption spectra, IPAS(λnormali), for diluted propane, ethane and methane test gases at low concentrations (c∼1000.166667emppm) were measured for ∼1350 discrete wavelengths λnormali. The IPAS(λnormali) spectra were then compared to the high resolution cross section data, σFTIR, 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 IPAS(λnormali) and the expected reference values based on σFTIR were recorded. The characteristic absorption wavelengths λres can be resolved with an average resolution of δλres∼0.080.166667emnm. 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.

Multicomponent gas sensors based on photoacoustic spectroscopy technology: A review

“…Among these, Optical parametric oscillators (OPOs) and super‐continuum (SC) lasers have emerged as two of the most promising broad‐spectrum light sources. OPOs use high‐quality nonlinear crystals to enable parametric amplification of high‐power pump laser sources, 96 which can provide superior spectral resolution, high output power, and broad tunable wavelengths (2–14 μm). Lamard L et al demonstrated a single longitudinal mode pulsed OPO laser 69 .…”

Applications of Near Infrared Photoacoustic Spectroscopy for Analysis of Human Respiration: A Review

“…A growing interest in PAS for the 2.5-5 µm region is represented by cw periodically poled lithium niobate optical parametric oscillators (PPLN-OPOs) at high power (several watts) level and narrow linewidth. OPOs are pumped by high power lasers and its outstanding features are wide-range wavelength tunability of the emitted radiation with high and stable output power levels, and an exceptional beam quality and these characteristics make OPOs very valuable for laser spectroscopy [65][66][67].…”

Fiber-Coupled Quartz-Enhanced Photoacoustic Spectroscopy System for Methane and Ethane Monitoring in the Near-Infrared Spectral Range

“…In that case, the absorption bands will consist of well separated lines that usually allow discriminating the absorption features from different components and obtaining independent calibration curves for each species. When broadband absorptions related to more structured molecules overlap each other, several algorithms based on multiple linear regressions, partial least squares or multivariate analysis can be implemented to quantify the concentration of each gas [18][19][20][21][22][23].…”