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Indexed by:Journal Papers

Date of Publication:2020-03-02

Journal:OPTICS EXPRESS

Included Journals:SCIE

Volume:28

Issue:5

Page Number:6618-6630

ISSN No.:1094-4087

Abstract:A high-sensitivity photoacoustic (PA) spectroscopy (PAS) system is proposed for dual enhancement from both PA signal excitation and detection by employing a miniaturized Herriott cell and a fiber-optic microphone (FOM). The length of the optical absorption path of the PA cell is optimized to similar to 374 mm with 17 reflections. The volume of the PA cell is only 622 mu L. The FOM is a low-finesse fiber-optic Fabry-Pdrot (FP) interferometer. The two reflectors of the FP cavity are formed by a fiber endface and a circular titanium diaphragm with a radius of 4.5 mm and a thickness of 3 mu m. A fast demodulated white-light interferometer (WLI) is utilized to measure the absolute FP cavity length. The acoustic responsivity of the FOM reaches 126.6 nm/Pa. Several representative PA signals of trace acetylene (C2H2) are detected to evaluate the performance of the trace gas detector in the near-infrared region. Experimental results show that the minimum detectable pressure (MDP) of the FOM is 3.8 mu Pa/Hz(1/2) at 110Hz. The noise equivalent minimum detection concentration is measured to be 8.4 ppb with an integration time of 100 s. The normalized noise equivalent absorption (NNEA) coefficient is calculated as 1.4x10 (-9) cm(-1)W.Hz(-1/2). (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement