Fiber-optic open-cavity Fabry-Perot interferometric sensor for ultrasonic detection

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.