A New 3-D-Printed Nondestructive H-Like Resonant Fiber-Optic Photoacoustic Sensor for High-Sensitivity Remote Gas Sensing

This article proposes a new 3-D-printed nondestructive H-like resonant fiber-optic photoacoustic sensor for high-sensitivity remote gas sensing. The sensor is composed of an H-like resonant photoacoustic cell, a silicon cantilever, and two single-mode fibers. These two single-mode fibers are located on one side of the buffer chamber, where one single-mode fiber serves as an excitation fiber for transmitting the excitation light for the CH4 gas (operating wavelength =1650.96 nm), and the other one acts as a detection fiber to transmit the broadband light and to receive the returned interference light. The silicon cantilever is located inside the H-like resonant photoacoustic sensor, which solves the problem that the traditional H-like resonant photoacoustic sensor has to destroy its resonant cavity structure for photoacoustic signal detection. The high-frequency resonant photoacoustic sensor and silicon cantilever acoustic detector have been designed using the finite element analysis method. A laser-based fiber optic photoacoustic spectroscopy (PAS) system has been established and successfully implemented for high-sensitivity trace CH4 remote sensing, and the sensor has a detection limit of 894 ppb for CH4. The all-fiber 3-D-printed nondestructive H-like resonant photoacoustic sensor features ipsilateral excitation detection, compact size, high sensitivity, and all-fiber optic connection, providing a new solution for remote measurement of space-constrained trace gases.