Dual diaphragm structure-based all-glass microphone with enhanced robustness and sensitivity using laser processing

In this paper, a novel and cost-effective all-glass microphone with enhanced sensitivity and robustness is introduced, enabled by dual diaphragm structure including pressure amplification diaphragm and acoustic sensing diaphragm. Pressure amplification diaphragm is applied to enhance external acoustic wave, with its focal plane located exactly on the plane of sensing diaphragm, thereby introducing enhanced deflection. Then acoustic introduced deflection is further interrogated interferometrically through the light transmitted by optical fiber. Multi-laser processing method is developed for all-glass microphone fabrication, where picosecond laser is applied for precise diaphragm micromachining and welding, and CO₂ laser is employed for fixing of optical fiber and fiber housing structure. Experimental results demonstrate that the proposed microphone with dual diaphragm achieves a 2.24- fold enhancement in sensitivity at resonant frequency, that is, 206.314 mV/Pa, with signal-to-noise ratio increased from 66.31 dB to 75.68 dB. With advantages of compact size, high sensitivity and enhanced robustness, the proposed all-glass microphone shows strong potential for harsh environment applications.