Luo Huijian, Li Junming, Lv Haohua, Xie Jiabao, Wang Chenglong, Lin Haoyang, Zhuang Ruobin, Zhu Wenguo, Zhong Yongchun, Kan Ruifeng, Yu Jianhui, Zheng Huadan
Opt Lett. 2024 Jun 1;49(11):3206-3209. doi: 10.1364/OL.506650.
In this work, we developed off-plane quartz-enhanced photoacoustic spectroscopy (OP-QEPAS). In the OP-QEPAS the light beam went neither through the prong spacing of the quartz tuning fork (QTF) nor in the QTF plane. The light beam is in parallel with the QTF with an optimal distance, resulting in low background noise. A radial-cavity (RC) resonator was coupled with the QTF to enhance the photoacoustic signal by the radial resonance mode. By offsetting both the QTF and the laser position from the central axis, we enhance the effect of the acoustic radial resonance and prevent the noise generated by direct laser irradiation of the QTF. Compared to IP-QEPAS based on a bare QTF, the developed OP-QEPAS with a RC resonator showed a >10× signal-to-noise ratio (SNR) enhancement. The OP-QEPAS system has great advantages in the use of light emitting devices (LEDs), long-wavelength laser sources such as mid-infrared quantum cascade lasers, and terahertz sources. When employing a LED as the excitation source, the noise level was suppressed by ∼2 orders of magnitude. Furthermore, the radial and longitudinal resonance modes can be combined to further improve the sensor performance.
在这项工作中，我们开发了离面石英增强光声光谱技术（OP-QEPAS）。在OP-QEPAS中，光束既不穿过石英音叉（QTF）的叉指间距，也不在QTF平面内。光束与QTF平行且保持最佳距离，从而降低背景噪声。一个径向腔（RC）谐振器与QTF耦合，通过径向共振模式增强光声信号。通过将QTF和激光位置都从中心轴偏移，我们增强了声学径向共振的效果，并防止了QTF受激光直接照射产生的噪声。与基于裸QTF的IP-QEPAS相比，带有RC谐振器的已开发OP-QEPAS的信噪比（SNR）提高了10倍以上。OP-QEPAS系统在使用发光器件（LED）、长波长激光源（如中红外量子级联激光器）和太赫兹源方面具有很大优势。当采用LED作为激发源时，噪声水平被抑制了约2个数量级。此外，径向和纵向共振模式可以结合起来进一步提高传感器性能。
