Gas sensing technology is applied across various fields, including environmental monitoring, industrial control, and medical diagnostics. The quartz tuning fork (QTF) serves as a detection element, offering advantages such as a high-quality factor, noise immunity, compact size, and low cost, while its resonant characteristics enhance system signal strength.
Two QTF-based spectroscopic techniques, Quartz-enhanced photoacoustic spectroscopy (QEPAS) and light-induced thermoelastic spectroscopy (LITES), are current research areas in spectral sensing.
Professor Yufei Ma and a team from the National Key Laboratory of Laser Spatial Information, Department of Electronic Science and Technology, Harbin Institute of Technology, China, have published a comprehensive review in Light: Science & Applications. This paper details and highlights innovations in QEPAS and LITES techniques.
For QEPAS, performance enhancement methods include: using high-power lasers for increased gas molecule absorption; applying novel excitation sources with strong absorption coefficients; utilizing custom QTFs to improve detected signals; and employing acoustic resonators or multi-pass structures to amplify acoustic waves.
Regarding LITES, efforts to optimize gas sensor sensitivity have focused on: improving optical absorption, often through cavity enhancement techniques; enhancing QTF detection performance via modification or custom QTFs; increasing system response speed by using QTF transient response to build heterodyne systems; and maximizing laser energy utilization by leveraging QEPAS technology advantages.
Future prospects for these technologies are also discussed, anticipating evolution towards higher sensitivity, increased integration (including on-chip), and greater ease of practical application through cross-disciplinary convergence.