In this manuscript, a high-sensitivity optical fiber Fabry-Perot sensor based on all-sapphire is proposed and fabricated for pressure sensing in ultra-high temperature environments. Compared with other works, the pressure-sensing sapphire wafer’s thickness was reduced to about 40 μm to improve the pressure sensitivity dramatically, while maintaining its dimensions to be 2mm×2mm. The double-side wet-etching process was adopted to thin the sapphire wafer. The roughness of the wetted sides was modified by different etching processes to optimize the optical interference fringe. The all-sapphire sensor head was assembled with a directed bonding method, and the sapphire fiber was adopted to be the lead-in fiber to increase the sensor’s tolerance to high temperatures. Detailed experiment shows that the fabricated sensor can work stably under 1200°C in the range of 0-3 MPa. The pressure sensitivity increased from 0.877 μm/MPa under room temperature to 1.193 μm/MPa under 1200°C. The good performance of the proposed sensor under high temperatures ensures its good application in pressure sensing of aero-engine, gas turbine, etc.

Accurate characterization of atomic vapor cells is crucial for enhancing the sensitivity of miniature atomic magnetometers. In this study, a fast and efficient approach is developed to characterize relaxation properties of the inner surface of the 87Rb micro-electro-mechanical systems (MEMS) vapor cell. Based on the zero-field level crossing effect, the transverse relaxation rate was experimentally determined, and the depolarization coefficient of 0.097 for atom-wall collisions in the 87Rb MEMS vapor cell was obtained. The experiments demonstrated that the alkali-wall collision relaxation gradually dominates the depolarization of the 87Rb ensemble as the radius of the vapor cell decreases. This research provides a quantitative method to evaluate the effectiveness of the MEMS vapor cell anti-relaxation coatings and offers the design inspiration for MEMS atomic vapor cells from the perspective of relaxation characterization. It is beneficial for the development of weak magnetic field detections such as biomagnetism detection in ambient environments.