Hourglass-Shaped Fiber-Optic Mach-Zehnder interferometer for pressure sensing

A fiber-optic pressure sensor based on an hourglass -shaped structure (HSS) is proposed and demonstrated. A Mach-Zehnder interferometer (MZI) is constructed in the inside cavity of the HSS. The HSS consists of a silica frame and two photoresist diaphragms covered on side holes of the frame. Pressure response of the MZI is analyzed by theoretical calculation, the mechanical deformation of the HSS is simulated by using the finite element method, and the spectral characteristics of the sensor are simulated by using the finite -difference beam propagation method. Experimental results indicate that the pressure sensitivity of the sensor with a size of 0.2 x 0.2 x 0.5 mm3 reaches -1.27 nm/kPa with a linear response range of 0-35 kPa. In addition, repeatability, time stability, the cross -responses to ambient refractive index (RI) and temperature, and response time of the sensor are evaluated experimentally. With advantages of high sensitivity, compact size, and insensitivity to ambient RI, the proposed sensor shows promising potential in optofluidic and biomedical sensing fields.