Bioinspired lab-on-fiber ultrasonic probe family with structurally differentiated resonant responses

Abstract

Fiber-optic ultrasonic probes with structurally differentiated resonant responses are needed for underwater acoustic sensing with high sensitivity and frequency selectivity. Inspired by the distributed organization of mechanically responsive sensing units in aquatic crustaceans, we present a microstructured fiber tip Fabry–Perot optomechanical ultrasonic probe family whose resonant responses are systematically differentiated across distinct ultrasonic bands through geometrically tailored coupling between the diaphragm and supporting beams. In this architecture, the folded supporting beams act as a geometry-defined elastic boundary of the diaphragm and participate directly in the pressure-induced cavity length variation through coupled support translation and diaphragm bending. Finite-element modeling established a resonant design framework, and three probes fabricated by two-photon polymerization were designed with distinct resonant frequencies of 174 kHz, 1.0 MHz, and 1.6 MHz. The simulated resonances remained within the same first-order diaphragm-dominated modes. Experiments confirmed that the probes exhibited clearly differentiated response bands. The 1 MHz probe exhibited a sensitivity of 0.971 V/kPa, a noise-equivalent pressure of 1.04 Pa, and a photoacoustic bandwidth of 31.52 MHz under a 20% peak amplitude criterion, together with stable pulse detection and wide angular response. Representative demonstrations validated transient acoustic perception and multiband burst recognition, where decision-level fusion increased the mean detection rate from 30.4%–67.3% to 95.4%. Underwater ultrasonic imaging was also demonstrated. This work establishes a structurally differentiated lab-on-fiber optomechanical architecture for compact optical ultrasound detection and optoacoustic microsystems.