Noncontact Fiber-Optic Cantilever-Enhanced Photoacoustic Spectroscopy

Conventional cantilever-enhanced photoacoustic spectroscopy (CEPAS) usually requires the cantilever to be in contact with the gas, which limits its application in dusty and corrosive gas sensing. To overcome this challenge, this paper proposes noncontact fiber-optic cantilever-enhanced photoacoustic spectroscopy (NCFO-CEPAS) for high-sensitivity trace gas analysis. A polyethylene film with corrosion-resistant properties is affixed to the end of the cantilever acoustic sensor, and the effect of the distance between the polyethylene film and the cantilever acoustic sensor on the sensitivity of the system is analyzed by finite element analysis. Compared to the conventional CEPAS, NCFO-CEPAS has a lower background noise deviation. Besides, the potential damage to the silicon cantilever beam by corrosive gases can be avoided as the gas to be measured is not in contact with the silicon cantilever beam, and the gap of the cantilever beam will not be blocked in a high dust environment. Experimental results show that the detection limit of C₂H₂ gas is 0.5 ppm, and the normalized noise equivalent absorption coefficient reaches 5.93 × 10^-9 cm^-1 W Hz^-1/2. The NCFO-CEPAS technique has the advantages of noncontact remote gas monitoring, not being corroded by gases, and high resistance to electromagnetic interference.