Demonstration of an All-Sapphire Fabry–Pérot Cavity for Pressure Sensing

This letter presents a first demonstration of a monolithic sapphire Fabry-Pérot (FP) cavity for pressure sensing. The prototype was constructed by combining reactive ion etching with direct wafer bonding. Long-term testing proves that the adhesive-free wafer bond is sufficient to create a sealed FP cavity as a pressure transducer. Pressure measurement over a range of 0.04-1.38 MPa has been demonstrated at room temperature using white-light interferometry. With an all-sapphire configuration, the prototype reported here can be further developed into a pressure sensor with high-temperature harsh-environment capability.