Folded-optics-based quartz-enhanced photoacoustic and photothermal hybrid spectroscopy

Ruyue Cui; Hongpeng Wu; Frank K Tittel; Vincenzo Spagnolo; Weidong Chen; Lei Dong

doi:10.1016/j.pacs.2023.100580

Folded-optics-based quartz-enhanced photoacoustic and photothermal hybrid spectroscopy

Photoacoustics. 2023 Dec 7:35:100580. doi: 10.1016/j.pacs.2023.100580. eCollection 2024 Feb.

Authors

Ruyue Cui^{1

2

3}, Hongpeng Wu^{1

2}, Frank K Tittel⁴, Vincenzo Spagnolo^{1

5}, Weidong Chen³, Lei Dong^{1

2}

Affiliations

¹ State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
² Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.
³ Laboratoire de Physicochimie de l'Atmosphère, Université du Littoral Côte d'Opale, Dunkerque 59140, France.
⁴ Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA.
⁵ PolySense Lab-Dipartimento Interateneo di Fisica, University and Politecnico of Bari, Via Amendola 173, Bari, Italy.

Abstract

Folded-optics-based quartz-enhanced photoacoustic and photothermal hybrid spectroscopy (FO-QEPA-PTS) is reported for the first time. In FO-QEPA-PTS, the detection of the photoacoustic and photothermal hybrid signal is achieved through the use of a custom quartz tuning fork (QTF), thereby mitigating the issue of resonant frequency mismatch typically encountered in quartz-enhanced photoacoustic-photothermal spectroscopy employing multiple QTFs. A multi-laser beam, created by a multi-pass cell (MPC) with a designed single-line spot pattern, partially strikes the inner edge of the QTF and partially passes through the prong of the QTF, thereby generating photoacoustic and photothermal hybrid signals. To assess the performance of FO-QEPA-PTS, 1 % acetylene is selected as the analyte gas and the 2f signals produced by the photoacoustic, the photothermal, and their hybrid effects are measured. Comparative analysis against QEPAS and QEPTS reveals signal gain factors of ∼ 79 and ∼ 14, respectively, when these laser beams created by MPC excite the QTF operating at fundamental resonance mode in phase. In the FO-QEPA-PTS signal, the proportions of the photoacoustic and the photothermal effects induced by the multiple beams are ∼7 % and 93 %, respectively.

Keywords: Multi-pass cell; Photoacoustic spectroscopy; Photothermal spectroscopy; Quartz tuning fork.