A miniaturized multi-mechanism resonance-enhanced fiber optic photoacoustic multi-gas sensor

A multi-mechanism resonance-enhanced fiber-optic photoacoustic multi-gas sensor (MR-FOPMS) is reported, in which the acoustic resonance of the T-type resonator is employed for C₂H₂ gas sensing and the mechanical resonance of the silicon cantilever is employed for the detection of CH₄ gas sensing. The silicon cantilever fiber-optic microphone and T-type photoacoustic resonator are designed using theoretical and finite element methods. The optimized cavity volume of the entire sensor is only 9.3 cm³ and the optimized silicon cantilever microphone has an ultra-high sensitivity of 62540.2 nm/Pa at the resonance. The ability of the sensor to detect multiple gases is demonstrated by simultaneous measurement of C₂H₂ and CH₄ using two DFB lasers at 1532.8 nm and 1650.96 nm as excitation sources. The lowest detection limits of the sensor are determined to be 158 and 382 ppb for C₂H₂ and CH₄, respectively, corresponding to normalized noise equivalent absorption coefficients of 2.82 × 10^-9, 1.43 × 10^-9 cm⁻¹ W Hz^−1/2, respectively.