High-Accuracy Wide-Range Gas Refractive Index Sensor Based on All-Solid Fabry-Pérot Interferometer

The gas refractive index (RI) sensors with wide measurement ranges and high sensing accuracy are urgently required for biomedical and industrial applications. Here, we propose an open Fabry-Perot interferometer (FPI) gas RI sensor, which is prepared by bonding three layers of titanium-silicate glasses together using light contact bonding technology to improve its structural strength. The medium’s RI within the FPI can be ascertained by measuring the spectral shift. The sensor has a sensitivity of 1527.2155 nm/RIU in the range of 1.000268627–1.026779627, with a relative error of 0.094% F.S. and an RI resolution of $1.3 \times 10^{-{5}}$ RIU, which allows it to meet the sensing needs of most gases. Furthermore, we investigate the high-temperature characteristics of the sensor and find that it has low temperature cross-sensitivity of 0.06 nm/°C in the range of 20 °C–200 °C. Therefore, the sensor is suitable for RI detection in the field of chemical industry, biosensing, and many harsh environments.