Biomimetic microstructured diaphragms enable high-sensitivity and wide-dynamic-range fiber-optic microphones

External cavity Fabry-Perot (EFPI) fiber optic microphones (FOMs) offer significant advantages in complex acoustic sensing environments. From a materials perspective, the core of an F-P type fiber optic microphone is its sensitive diaphragm. However, traditional planar diaphragms typically require a balance between mechanical compliance and structural stability, necessitating improvements to the sensitive diaphragm of fiber optic microphones. Inspired by the efficient auditory mechanisms of insects, this paper proposes and demonstrates a series of high-performance EFPI fiber optic microphones employing biomimetic microstructured silicon nitride (Si3N4) diaphragms. Three different microtopologies—concentric corrugations, radial stripes, and two-dimensional honeycombs—were proposed, and after theoretical analysis, were precisely manufactured using advanced micro-opto-electro-mechanical systems (MOEMS) etching technology. A novel, precise optomechanical coupling strategy was employed during the microphone’s coupling and packaging process to achieve optimal free spectral range (FSR) and extinction ratio (ER) for each specific topology. Acoustic testing results demonstrate that these biomimetic structural designs effectively optimize the mechanical strain threshold and compliance of the silicon-based diaphragm. The radial stripe FOM achieves an outstanding sensitivity of 1278.3 mV/Pa, an ultra-low minimum detection pressure (MDP) of 0.36 mPa, and a high acoustic overload point of 103.02 dBSPL. The concentric corrugated FOM exhibits excellent broadband spectral smoothness and uniformity, while the two-dimensional honeycomb FOM demonstrates superior modal equalization and high-frequency harmonic suppression capabilities. In summary, all three biomimetic microstructures exhibit ultra-high sensitivity, wide dynamic range, and excellent small-signal detection capabilities, laying a solid foundation for developing high-sensitivity passive acoustic sensor arrays for industrial monitoring and robot spatial positioning.