A Fabry–Pérot interferometer strain sensor composed of a rounded rectangular air cavity with a thin wall for high sensitivity and interference contrast

A Fabry–Pérot interferometer (FPI) strain sensor with high sensitivity and interference contrast is designed and fabricated by a simple, cost effective, and safe process which can be scaled up for commercial production. The excellent strain sensitivity of 8 pm/μ ɛ and interference contrast of 25 dB stem from the special structure with the unique air cavity, small wall thickness, and excellent reflection surface of the air cavity. The strain-temperature cross-sensitivity of the sensor is only 0.59 μ ɛ/°C in the temperature range of 20–80°C. The sensor has large potential in applications such as strain sensing.