Mie resonance metasurface-enhanced laser-induced acoustic transducer for directional radiation

Laser-induced acoustics enables the generation of acoustic waves through laser-induced breakdown in transparent media and provides an effective approach for air–water cross-medium signal conversion. To improve energy utilization and spatial controllability, laser-induced acoustic directional radiation transducers have been proposed. However, conventional transducer designs still exhibit limited capability in modulating low-frequency acoustic waves with high directivity. In contrast, artificial acoustic metamaterials offer unique degrees of freedom for manipulating acoustic wave propagation. In this study, a double hemispherical reflective surface laser-induced acoustic transducer integrated with a Mie-resonance metasurface is proposed to achieve enhanced low-frequency directional radiation and energy conversion efficiency. The dual reflective structure enables iterative acoustic reflections to improve beam collimation, while the Mie-resonant metasurface further refines the radiation directivity and suppresses transmission attenuation. Numerical simulations show that the normalized sound intensity amplitude remains above 0.7 over a propagation distance of five wavelengths (370 cm), demonstrating stable low-frequency directional radiation and long-distance transmission with minimal energy loss. The compact system employs epoxy-resin-based Mie resonant units with a radius of 135 mm, operating at 2070 Hz (λ ≈ 0.74 m). This integration of acoustic metasurfaces with laser-induced acoustic transducers provides an effective strategy for realizing highly efficient, low-frequency, and long-range directional acoustic sources, offering a promising technological framework for underwater communication and cross-media information transmission.