- Accepted Paper
Subwavelength ultrasonic imaging by extraordinary transmission in solids
Phys. Rev. Applied - Accepted 9 October, 2026
DOI: https://doi.org/10.1103/8z7c-ddxb
Phys. Rev. Applied - Accepted 9 October, 2026
DOI: https://doi.org/10.1103/8z7c-ddxb
Far-field ultrasonic imaging is fundamentally limited by the diffraction limit: increasing frequency improves lateral resolution by focusing but at the cost of higher attenuation and fabrication difficulty. In contrast, metamaterial-based strategies offer a route to non-contact near-field subwavelength concentration and improved resolution without resorting to higher operating frequencies. In this paper, we demonstrate a subwavelength acoustic resonant system for near-field ultrasonic imaging at 500 kHz based on extraordinary acoustic transmission, or EAT, of bulk waves inside a solid. Combining a Fabry–Perot resonant subwavelength-diameter aluminum pillar with concentric grooves engineered to convert bulk waves into Rayleigh surface waves allows the concentration of elastic waves to a subwavelength spot at the pillar apex. Pulse–echo experiments demonstrate near-field contrast in the round-trip transmission response of the subwavelength structure, with finite-element simulations linking this response to field localization at the pillar apex. Near-field scans of test samples with a water-layer couplant then reveal the quantitative retrieval of subwavelength object features, with a two-dimensional lateral resolution of ~1 mm, corresponding to ~1/12 of the longitudinal wavelength in aluminum. These results establish solid-state EAT metamaterials as a robust alternative approach to ultrasonic imaging, opening the way to advanced probe designs and near-surface inspection applications.
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