Abstract
Development of novel mid-infrared (MIR) lasers could ultimately boost emerging detection technologies towards innovative spectroscopic and imaging solutions. Photoacoustic (PA) modality has been heralded for years as one of the most powerful detection tools enabling high signal-to-noise ratio analysis. Here, we demonstrate a novel, compact and sensitive MIR-PA system for carbon dioxide (CO2) monitoring at its strongest absorption band by combining a gas-filled fiber laser and PA technology. Specifically, the PA signals were excited by a custom-made hydrogen (H2) based MIR Raman fiber laser source with a pulse energy of ⁓ 18 μJ, quantum efficiency of ⁓ 80% and peak power of ⁓ 3.9 kW. A CO2 detection limit of 605 ppbv was attained from the Allan deviation. This work constitutes an alternative method for advanced high-sensitivity gas detection.
Highlights
Development of novel mid-infrared (MIR) lasers could boost emerging detection technologies towards innovative spectroscopic and imaging solutions
The MIR pulses are generated through the vibrational stimulated Raman scattering (SRS) by using H2 as nonlinear propagation medium, which is pressurized in the hollow region of anti-resonant hollow-core fibers (ARHCF) and can directly red-shift the near-infrared pump line to mid-infrared region due to its large Raman shift coefficient of 4155 cm−1
Pertaining to the unique features of the PA-based gas detection approach, it is shown that the use of a MIR high pulse energy and peak power H 2-filled Raman fiber laser acts as a new element that significantly scales up the performance of a PA system and creates new research directions towards gas spectroscopy and microscopy[19]
Summary
Development of novel mid-infrared (MIR) lasers could boost emerging detection technologies towards innovative spectroscopic and imaging solutions. Its underlying mechanism relies on the photo-excited acoustic signals that linearly vary as a function of the absorbed laser power This emerging tool has been presently established within industrial gas analysis sector because compared with other optical detection schemes, it possesses unique advantages such as high-sensitivity, wide-dynamic range, short optical path length (compact size), and near-tozero background s ignal[21,22,23,24,25,26,27]. The ability to combine active Raman gases—as the nonlinear medium—with the recently developed low-loss anti-resonant hollow-core fibers (ARHCF) platform allowed the scientific community to move gas-based nonlinear optics to remarkable and previously inaccessible parameter regimes of high intensity with MHz level b andwidths[32], and create a desirable solution for the generation of high peak power and high-energy laser pulse in the UV and MIR, Scientific Reports | (2021) 11:3512. The MIR PA scheme presented in this paper, offers a flexible selection of laser parameters with respect to the targeted trace gas detection application and promises a new tool for PA imaging and spectroscopy
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