Multi-pass enhanced photoacoustic sensor for open gas sensing.

In this paper, a photoacoustic trace gas sensor based on a multi-pass enhanced open spherical photoacoustic cell (M-OPAC) was developed. A high-performance spherical photoacoustic (PA) cell was specially designed with high resonant frequency for suppressing various environmental noises, and integrated with a Herriot-type multi-pass optical system for enhancing PA signal. For evaluating the developed PA sensor system, details of theoretical simulation and experimental test were investigated for ambient water vapor (H2O) detection by utilizing a DFB diode laser with a central wavelength of 1391 nm, and wavelength modulation spectroscopy with second harmonic (WMS-2f) detection technique was employed. Compared to the conventional single-pass PA detection strategy, the developed multi-pass PA sensor shows a sensitivity enhancement of 4.3 times and demonstrates a good immunity to ambient noises. Moreover, the developed spherical open photoacoustic cell can be used for open monitoring of atmospheric adsorbent gases, which indicates a great potential for in-site and real-time gas monitoring without complex gas sampling procedures. [ABSTRACT FROM AUTHOR]