Ye Weilin, He Linfeng, Liu Weihao, Yuan Zhile, Zheng Kaiyuan, Li Guolin
Shantou Key Laboratory for Intelligent Equipment and Technology, College of Engineering, Shantou University, 243 Dax-ue Road, Shantou 515063, PR China.
Key Laboratory of Intelligent Manufacturing Technology, Ministry of Education, College of Engineering, Shantou University, 243 Daxue Road, Shantou 515063, PR China.
Photoacoustics. 2024 Dec 9;41:100677. doi: 10.1016/j.pacs.2024.100677. eCollection 2025 Feb.
Traditional beat frequency quartz-enhanced photoacoustic spectroscopy (BF-QEPAS) are limited by short energy accumulation times and the necessity of a decay period, leading to weaker signals and longer measurement cycles. Herein, we present a novel optomechanical energy-enhanced (OEE-) BF-QEPAS technique for fast and sensitive gas sensing. Our approach employs periodic pulse-width modulation (PWM) of the laser signal with an optimized duty cycle, maintaining the quartz tuning fork's (QTF) output at a stable steady-state level by applying stimulus signals at each half-period and allowing free vibration in alternate half-periods to minimize energy dissipation. This method enhances optomechanical energy accumulation in the QTF, resulting in an approximate 33-fold increase in response speed and a threefold increase in signal intensity compared to conventional BF-QEPAS. We introduce an energy efficiency coefficient to quantify the relationship between transient signal amplitude and measurement duration, exploring its dependence on the modulation signal's period and duty cycle. Theoretical analyses and numerical simulations demonstrate that the maximum occurs at a duty cycle of 50 % and an optimized beat frequency Δ of 30 Hz. Experimental results using methane reveal a detection limit of 2.17 ppm with a rapid response time of 33 ms. The OEE-BF-QEPAS technique exhibits a wide dynamic range with exceptional linearity over five orders of magnitude and a record noise-equivalent normalized absorption (NNEA) coefficient of 9.46 × 10 W cm Hz. Additionally, a self-calibration method is proposed for correcting resonant frequency shifts. The proposed method holds immense potential for applications requiring fast and precise gas detection.
传统的拍频石英增强光声光谱技术（BF-QEPAS）受到能量积累时间短和需要衰减期的限制，导致信号较弱且测量周期较长。在此，我们提出了一种用于快速灵敏气体传感的新型光机械能增强（OEE-）BF-QEPAS技术。我们的方法采用具有优化占空比的激光信号周期性脉宽调制（PWM），通过在每个半周期施加激励信号，使石英音叉（QTF）的输出保持在稳定的稳态水平，并在交替的半周期允许自由振动以最小化能量耗散。这种方法增强了QTF中的光机械能积累，与传统的BF-QEPAS相比，响应速度提高了约33倍，信号强度提高了三倍。我们引入了一个能量效率系数来量化瞬态信号幅度与测量持续时间之间的关系，探讨其对调制信号周期和占空比的依赖性。理论分析和数值模拟表明，最大能量效率系数出现在占空比为50%且优化拍频Δ为30Hz时。使用甲烷的实验结果显示检测限为2.17ppm，响应时间快速，为33ms。OEE-BF-QEPAS技术具有宽动态范围，在五个数量级上具有出色的线性度，记录的噪声等效归一化吸收（NNEA）系数为9.46×10 W cm Hz。此外，还提出了一种用于校正共振频率偏移的自校准方法。该方法在需要快速精确气体检测的应用中具有巨大潜力。
