3D Acoustic Imaging Hitting the Diffraction Limit via Fully Parameter-Optimized Meta-Lens and Frequency-Domain Reconstruction.

Li, Zong-Lin; Huang, Lai-Xin; Sun, Qi-Li; Zhao, Yong-Jian; Li, Peng-Qi; Peng, Yu-Gui; Zeng, Long-Sheng; Zhou, Juan et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Super-resolution imaging is the long-sought goal pursued in acoustics. In the past decade, many solutions have been proposed by utilizing various metamaterial devices. For example, in acoustics, the holographic meta-lens is employed to improve the lateral resolutions of ultrasonic imaging. However, the filtering effect of meta-lens broadens the acoustic wave pulses, which severely degrades longitudinal resolutions, making the high-resolution 3D imaging hitherto quite challenging. Here, an innovative solution is proposed by designing and implementing a fully parameter-optimized meta-lens. At the fundamental frequency, this meta-lens can achieve a lateral resolution of 80 µm (≈0.37λ<sub>0</sub>), successfully breaking the diffraction limit. Through the frequency-domain reconstruction, the longitudinal resolution is increased to 296 µm (≈1.36λ<sub>0</sub>). Utilizing the nonlinear effect of ultrasound in water, the acoustic meta-lens can furtherly optimize its imaging quality at the harmonic frequency, where the lateral resolution is increased to 44 µm (≈0.2λ<sub>0</sub>) with the longitudinal resolution to 148 µm (≈0.68λ<sub>0</sub>). The work breaks the bias on meta-lenses with deteriorated longitudinal resolution for broad applications in functional ultrasonic imaging.