Dual-tube MEMS-based spectrophone for sub-ppb mid-IR photoacoustic gas detection
Stefano Dello Russo, Jacopo Pelini, Inaki Lopez Garcia, Mariaconcetta Canino, Alberto Roncaglia, Pablo Cancio Pastor, Iacopo Galli, Paolo De Natale, Simone Borri, Mario Siciliani de Cumis
Abstract
Nowadays, the scientific community and industry are increasingly pressed to provide solutions for developing compact and highly-performing trace-gas sensors for several applications of crucial importance, such as environmental monitoring or medical diagnostics. In this context, this work describes a novel configuration, making use of a mid-IR spectrophone combining the compactness of a photo-acoustic setup, a non-conventional micro-electro-mechanical (MEMS) acousto-to-voltage transducer, and the sensitivity enhancement given by a cost-effective and easy-to-build dual-tube resonator configuration. In the optimal condition of sample pressure, the system developed in this work can achieve a minimum detection limit (MDL) equal to 0.34 ppb when averaging up to 10 s. Compared with previous literature of single-pass photoacoustic-based sensors for N 2 O, this corresponds to a significant improvement both for the achieved normalized noise equivalent absorption coefficient (NNEA) equal to 1.41 × 10 − 9 cm − 1 WHz − 1 / 2 , and for a Noise-Equivalent-Concentration (NEC) of 1 ppb obtained at 1 s of averaging time.