Deep-Subwavelength-Scale Directional Sensing Based on Highly Localized Dipolar Mie Resonances

Acoustic waves are key to applications involving underwater communication and sonar, for example. Directional sensing of low-frequency (long-wavelength) sound is hampered, however, by the diffraction limit, which would necessitate inconveniently large (and probably immobile) detectors. The authors use the bounded metasurface surrounding a particle's rigid core to modulate acoustic pressures by an order of magnitude. Angle-dependent dipolar resonances allow direction-sensitive detection of plane waves, despite that the structures are far smaller than the wavelength.