Mid-infrared swept cavity-enhanced photoacoustic spectroscopy using a quartz tuning fork

Year: 2023

Authors: Nie QX., Wang Z., Borri S., Natale PD., Ren W.

Autors Affiliation: Chinese Univ Hong Kong, Dept Mech & Automat Engn, Shatin, Hong Kong, Peoples R China; CNR INO, Ist Nazl Ott, I-50019 Sesto Fiorentino, Italy; European Lab Nonlinear Spect, LENS, I-50019 Sesto Fiorentino, Italy.

Abstract: We report the development of swept cavity-enhanced photoacoustic spectroscopy using a quartz tuning fork for ultra-sensitive and high-resolution molecular spectroscopy. By using a quantum cascade laser (QCL) as the mid-infrared light source, a dual-feedback Pound-Drever-Hall locking method is proposed to lock the QCL frequency to a continuously swept optical cavity. By placing an off-beam quartz-enhanced photoacoustic spectroscopy module in a 48-mm Fabry-Perot cavity, we are able to achieve ultra-sensitive gas detection based on the doubly resonant photoacoustic effect. As a proof-of-concept, we use a distributed feedback QCL to exploit the CO line at 2190.02 cm(-1), where the cavity-locked QCL is scanned over a spectral range of 10 GHz with a spectral resolution of & SIM;3 MHz. With the incident laser power of 7.3 mW, the optical cavity (finesse 1931) builds up the intracavity power beyond 3 W. Our photoacoustic spectrometer achieves the minimum detection limit of 375 part-per-trillion (ppt) at the averaging time of 150 s and the normalized noise equivalent absorption coefficient of 1.27 x 10(-9) Wcm(-1) Hz(-1/2).

Journal/Review: APPLIED PHYSICS LETTERS

Volume: 123 (5)      Pages from: 54102-1  to: 54102-5

More Information: This research was supported by the General Research Fund (GRF) (No. 14208221) from the University Grants Committee and Innovation and Technology Fund (ITF) (No. GHP/129/20SZ), Hong Kong SAR, China. The authors would also like to acknowledge the financial support by Laserlab-Europe V (Horizon 2020) program under Grant Agreement No. 871124, and the European Union’s Next Generation EU Program with the I-PHOQS Infrastructure [Nos. IR0000016, ID D2B8D520, and CUP B53C22001750006] Integrated infrastructure initiative in Photonic and Quantum Sciences. The authors thank Dr. Ying He for assistance with the fabrication of the QEPAS module.
KeyWords: Quantum Cascade Laser; Carbon-monoxide; Absorption-spectroscopy; Gas-detection; Co Detection; Sensor
DOI: 10.1063/5.0159131

Citations: 12
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