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<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub>, based on silicone gel (Sg) thin film, and a capillary-based reference element, FPI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub>. In the range of 0-0.3 Mpa, three sensing FPI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> 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<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> were fabricated for parallelling to the three FPI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> 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<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub>. 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<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> HVE-based sensors has been significantly reduced for no need of precise control of cavity length of FPI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> and FPI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub>. 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.