Capacitive microelectromechanical system microphone in a small package encounters performance limits associated with damping in the air gap between diaphragm and backplate. In this work, we explored optical-readout technique by fabrication of an optical interferometric acoustic sensor. The designed sensor chip forms a grating interferometer by a diffraction grating integrated backplate and a pressure sensitive diaphragm. Scalar diffraction theory and finite element method have been applied to optimize the sensor parameters. The sensor device was fabricated on a silicon-on-insulator wafer using complementary metal–oxide–semiconductor compatible processes. The performance of the sensor was studied using an acoustic testing system. The sensor demonstrates a good linear relationship with applied sound pressure. The frequency response is relatively consistent with a commercial reference microphone for audible range. The signal to noise ratio of the sensor is about 43 dB at frequency of 1 kHz. The proposed design shows good potential for high performance acoustic sensor.

Hydrogen sulfide (H ₂ S) exists widely in many industrial processes and natural environments. Due to its high toxicity and flammable, detection of H ₂ S is critical for safety and health at work place and industrial process control. In this paper, we report a novel miniature gas sensor, which has a high selectivity in H ₂ S detection. The sensor is based on the principle of silver reacting with H ₂ S with a strict condition and a fast speed at high temperature. The limit of detection (LOD) is 1.4 parts-per-million (ppm) in ambient conditions, and can be further reduced to ~ppb-lever by improving working temperature and suppressing the noise of the sensor system. Compared with the conventional H ₂ S sensors, this sensor has advantages of miniaturization, low cost, high selectivity, and excluding electrolytes in the analyte detection.

Active metasurfaces, whose optical properties can be tuned by an external stimulus such as electric or laser pulses, have attracted great research interest recently. The phase change material (PCM), antimony sulfide (Sb₂S₃), has been reported to modulate resonance wavelengths from the visible to the infrared. Here, we present a purely numerical study of an active and nonvolatile narrow-band perfect absorber in the infrared region based on a nanostructured metal–insulator–metal (MIM) metasurface incorporating Sb₂S₃. The proposed absorber exhibits a high quality factor and achieves near-unity absorption at resonance wavelengths. In addition, the absorption spectrum can be dynamically modulated by the phase transition of Sb₂S₃, with a modulation range approaching 1 μm. Moreover, the designed absorber shows insensitivity to the angle of incidence. This study offers a feasible strategy for developing Sb₂S₃-integrated metasurface perfect absorbers with potential applications in selective thermal emitters and bolometers.

We report a method of precise chemical sensing by using on-chip external cavity lasing technology, in which a photonic micro-disk resonator acting as a sensing element is embedded into a laser’s external cavity. The bandwidth of resonance peak of the passive resonator is greatly reduced. The lasing technology improves the quality factor of the system and the detection limitation in chemical sensing by 1-order of magnitude comparing with conventional passive devices.