Li Zhengang, Liu Jiaxiang, Si Ganshang, Ning Zhiqiang, Fang Yonghua
Opt Express. 2022 Aug 1;30(16):28984-28996. doi: 10.1364/OE.465161.
A high-sensitivity differential Helmholtz photoacoustic cell based on multiple reflection was reported, and its performance parameters and gas replacement time were optimized by finite element simulation. To realize the long absorption path of the measured gas, the collimated excitation light was reflected multiple times on the gold-plated wall of the absorption cavity, and the wavelength modulation technology was used to reduce the multiple reflection noise. Additionally, the differential could suppress external co-phase noise and double the photoacoustic signal. When a laser with a central wavelength of 1653 nm was employed as the excitation light source, the minimum detection limit of 177 ppb (signal-to-noise ratio, SNR = 1) for methane was achieved within a detection time of 1 s, and the corresponding normalized noise equivalent absorption coefficient was 4.1×10 cmWHZ.
报道了一种基于多次反射的高灵敏度差分亥姆霍兹光声池，并通过有限元模拟对其性能参数和气体置换时间进行了优化。为实现被测气体的长吸收路径，准直激发光在吸收腔的镀金壁上多次反射，并采用波长调制技术降低多次反射噪声。此外，差分结构可抑制外部同相噪声并使光声信号加倍。当采用中心波长为1653 nm的激光作为激发光源时，在1 s的检测时间内实现了甲烷的最低检测限为177 ppb（信噪比，SNR = 1），相应的归一化噪声等效吸收系数为4.1×10 cmWHZ。
