Highly sensitive pressure sensors based on Fabry-Perot interferometers and Vernier effect

Based on the traditional Vernier effect (TVE) and harmonic Vernier effect (HVE) mechanisms, this paper studies high-sensitivity pressure sensors made by parallelling a sensing element of Fabry-Perot interferometer (FPI), FPI_s, based on silicone gel (Sg) thin film, and a capillary-based reference element, FPI_r. In the range of 0-0.3 Mpa, three sensing FPI_s were fabricated and tested with sensitivity range of 4.07 - 6.75 nm/Mpa. The affection of the thickness of the Sg film to the response to pressure was discussed. Three FPI_r were fabricated for parallelling to the three FPI_s to form four TVE or HVE-based sensors showing pressure sensitivity in the range of 51.26-197.06 nm/Mpa with good linearity. These sensors are of low temperature crosstalk. The highest sensitivity of theses sensors is about 48.41 times higher than that of a single FPI_s. It can be seen that, for the same harmonic order, the detuning is decreased, the M-factor and sensitivity are significantly improved. Experimental results shows that manufacturing difficulty of 1^st HVE-based sensors has been significantly reduced for no need of precise control of cavity length of FPI_r and FPI_s. According to the sensitivity requirements in actual situations, these proposed pressure sensors, have potential applications in different scenarios, such as healthcare, environmental monitoring, aerospace, and geological exploration.