High-Sensitivity Sapphire Vacuum Fiber Pressure Sensor for High Temperature Applications

A high-sensitivity sapphire extrinsic Fabry-Perot (FP) interferometer (EFPI) is proposed for the high-resolution pressure measurement in high temperature vacuum environment. A composite FP cavity structure is fabricated by directly bonding three sapphire wafers with different thickness to simultaneously measure temperature and pressure, which can effectively address the cross-sensitivity problem from temperature to pressure. Experimental results show that the pressure can be accurately measured from 0 to 100 kPa within the temperature range of 29 °C–800 °C. The optical cavity length (OCL) of the sealed air cavity varies linearly with pressure, and the pressure sensitivity increases with temperature, resulting in a maximum error of 4.3 kPa. The pressure sensitivities are 56.22 and 63.24 nm/kPa at room temperature and 800 °C, and the resolutions of pressure measurement are 17.79 and 15.81 Pa, respectively. Based on its excellent performance, the proposed high-sensitivity EFPI is a prospective sensor for measuring the vacuum pressure in high temperature environment.