A sensitivity-enhanced open-cavity fiber-optic Fabry-Perot interferometric sensor based on polydimethylsiloxane (PDMS) diaphragm is proposed and experimentally demonstrated for ultrasonic detection. Moreover, two central-symmetry circular holes are drilled onto the PDMS diaphragm by femtosecond micromachining. The open cavity can not only balance the pressure difference but also lead to the concentrated diaphragm vibration area in the center of the diaphragm, thus improving the diaphragm deformation. The experimental testing results show that the response peak-to-peak voltage of the PDMS diaphragm with dual circular holes is 35 % higher than that of the PDMS without holes. The proposed low-cost micro-device sensor provides high sensitivity and wideband response, which can be a good candidate for ultrasonic detection applications.
A Fabry–Perot interferometer (FPI) for CO2 gas sensing at atmospheric pressure is proposed and experimentally demonstrated. The gas sensing material is poly(ethyleneimine) (PEI)/poly(vinylalcohol) (PVA) compound, which exhibits reversible refrative index change upon absorption and release of CO2 gas molecules. The FPI is fabricated by coating a PEI/P VA film with a thickness of 15μm film at the end face of a single-mode fiber (SMF). A well-confined interference spectrum with fringe contrast of 19.5 dB and free spectra range (FSR) of 33.15 nm is obtained. The proposed FPI sensor is sensitive to the CO2 gas concentration change, and a sensitivity of 0.2833nm/PCT is obtained. The FPI sensor provides a solution in the development of low-cost and compact gas sensors for CO2 leakage monitoring.
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