Abstract

An all-optical photoacoustic spectroscopy based on lock-in white-light interferometry is proposed for trace gas detection. The cavity length of the fiber-optic Fabry–Perot cantilever microphone is demodulated by a high-speed white-light interferometer, whose spectral sampling is synchronously triggered by a phased locked signal. To improve the signal-to-noise ratio, the demodulated digital photoacoustic signal is further processed by a specially designed virtual lock-in amplifier. The designed photoacoustic spectrometer has been tested for trace acetylene (${\mathrm{C}}_2{\mathrm{H}}_2$) detection in the near-infrared region. The normalized noise equivalent absorption coefficient for ${\mathrm{C}}_2{\mathrm{H}}_2$ is achieved to be $1.1\times {10}^{-9}{\mathrm{cm}}^{-1}\mathrm{W}{\mathrm{Hz}}^{-1/2}$.

© 2018 Optical Society of America

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