LAUSR

Abstract A miniature single-fiber photoacoustic (PA) sensor was designed and proposed for the detection of trace amount of methane gas. A Fabry-Perot (FP) interferometric cantilever was used to monitor the PA signal generated by the methane gas having absorbed the laser energy. Therefore, a pump laser and a probe light source were required in this system and coupled by a wavelength division multiplexer (WDM) to transmit in only one fiber. A communal cavity utilized both as the FP cavity and the PA cell was designed and optimized. The principles behind the determination of the cell size were explored. The single-fiber and the communal cavity contributed to the small volume of the cell, which was calculated to be only ∼1.7 μ L . Experiments were designed to verify the practicability of the PA sensor. Operating at the resonant frequency of 1648 Hz, the real-time response time was measured to be ∼23 s. The minimum detectable limit (MDL) was 8.4 ppm with a 1 s lock-in integral time.