Fabry-Perot Interferometer Based on an Aluminum-Polyimide Composite Diaphragm Integrated With Mass for Acceleration Sensing

This study proposes a miniature and highly sensitive Fabry-Perot interferometer (FPI) based on aluminum - polyimide diaphragm integrated with a mass block for acceleration sensing. The composite diaphragms with a radius and thickness of 3.5 mm and 630 nm are manufactured by Micro-Electro-Mechanical System (MEMS) technology. To increase the adhesion of the polyimide diaphragm to silicon wafer and improve the quality of deflectable diaphragm, a 30-nm-thick aluminum diaphragm is first coated on the silicon wafer by magnetron sputtering; a silicon wafer in the intermediate diaphragm is reserved as a mass block to form an integrated structure. Air cavity of the FPI formed by this composite diaphragm is modulated via external vibration signals, leading to a variation in the length of the cavity. Three fiber optic Fabry–Perot accelerometers (FOFPAs) are fabricated with a measured average sensitivity and acceleration resolution of 2.6 V/g (100 Hz–3.2 kHz) and $4.12~\mu \text{g}$ /Hz $^{\mathrm {1/2}}$ respectively, which show high consistency and manufacturing reproducibility. Good heat resistance performance of the sensor below 280° can also be observed obviously. Thus, this proposed sensor is anticipated to have wide application prospects in micro vibration monitoring in high temperature.