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Signal and noise analysis in resonant photoacoustic spectroscopy using fast Fourier transform

A simple method based on fast Fourier transform (FFT) is used to analyze the signal and noise in resonant photoacoustic spectroscopy. Varying the sampling time, the photoacoustic signal and noise are analyzed using FFT method, and compared with lock-in amplifier method. A detection limit of 1 ppm of methane has been achieved in pure nitrogen using a 1653 nm laser with an average power of 3.6 mW.