This article presents a sapphire-based Fabry–Perot acoustic sensor with potential for application in harsh environment acoustic sensing. The key component of the sensor is a thin sapphire diaphragm with a diameter of 20 mm and thickness down to 10 proposed Au–Au bonding-associated lapping and polishing technique. Microfabrication characterizations have corroborated the availability of realizing wafer-class thin sapphire diaphragm fabrication by employing the Au–Au bonding-associated lapping and polishing technique, and the diaphragm can be then easily transferred and assembled as a sensor. The strategy for optimizing the stripping phenomenon during lapping is also proposed. Acoustic calibration experiment through a plane wave tube indicates the sensitivity of 13.58 mV/Pa at 10 kHz and the frequency response range of 100250 kHz. The temperature tolerance experiment through the muffle furnace shows that no structural damage or optical spectrum invalidity occurs even if the environmental temperature reaches 800°, which indicates a high working temperature of the sensor up to 80°. Major findings and future application directions of this article are concluded as: 1) realization of an innovative sapphire-based Fabry–Perot acoustic sensor that shows significant potential in applications of numerous key industrial domains, such as aerospace engineering, and 2) a novel approach for achieving wafer-class sapphire ultrathin diaphragm fabrication, which might offer innovative methods for the optimization of sapphire-based harsh environment sensors and give reference to the sapphire lapping process as demanded in the gallium nitride (GaN)-based light-emitting diodes (LED) industry.

Antenna miniaturization technology has been a challenging problem in the field of antenna design. The demand for antenna miniaturization is even stronger because of the larger size of the antenna in the low-frequency band. In this paper, we consider MEMS magnetoelectric antennas based on mechanical resonance, which sense the magnetic fields of electromagnetic waves through the magnetoelectric (ME) effect at their mechanical resonance frequencies, giving a voltage output. A 70 μm diameter cantilever disk with SiO₂/Cr/Au/AlN/Cr/Au/FeGaB stacked layers is prepared on a 300 μm silicon wafer using the five-masks micromachining process. The MEMS magnetoelectric antenna showed a giant ME coefficient is 2.928 kV/cm/Oe in mechanical resonance at 224.1 kHz. In addition, we demonstrate the ability of this MEMS magnetoelectric antenna to receive low-frequency signals. This MEMS magnetoelectric antenna can provide new ideas for miniaturization of low-frequency wireless communication systems. Meanwhile, it has the potential to detect weak electromagnetic field signals.

This paper presents a guided-mode resonance (GMR) reflector for sapphire based Fabry-Perot (F-P) sensors that enables tunable or wideband high reflectance with high temperature resistance, which is expected to effectively regulate the performance of F-P sensors and offer a novel approach for designing F-P sensors in harsh environments. Intrinsic and extrinsic GMR gratings are proposed, and their optical and thermal properties are investigated and compared through numerical simulations, such as rigorous coupled-wave analysis and finite element analysis methods. The quantitative results indicate high feasibility for harsh environment applications and the potential for adopting different demodulation methods. Significant enhancement in the F-P sensor performance is obtained through analysis based on the F-P interference model, and the spectrum fineness and sensor sensitivity can be enhanced by at least one order of magnitude. The GMR reflector can be extended to other types of F-P sensors, demonstrating significant potential in high-temperature applications.