Far‐Field Ultrasound Imaging with Subwavelength Resolution through Heterogeneous Medium Using Metagrating Illumination.

Ultrasound imaging technology is crucial for diagnostics in both biomedical and industrial fields. However, pushing the boundaries of resolution and overcoming difficulties presented by complex environments remain challenging. Traditionally, diffraction limits resolution due to the loss of valuable subwavelength information carried by evanescent waves. Scattering further complicates imaging through intricate materials or obstructions. Here, we presented an approach for achieving far‐field subwavelength resolution ultrasound imaging through heterogeneous mediums is presented. This method converts inaccessible evanescent wave into detectable propagating waves. These waves are then captured by a far‐field hydrophone and use in conjunction with the joint‐sparsity algorithm to reconstruct the object. These results demonstrate a remarkable resolution of 1/5λ, significantly surpassing the diffraction limit. This subwavelength imaging performance exhibits remarkable stability even in the presence of unwanted scatterers. The two‐dimensional imaging results and the influence of measurement parameters are further explored. These findings suggest that the combination of metagrating illumination and the joint‐sparsity algorithm offers a promising avenue for recovering subwavelength object information in the far‐field, eliminating the need for near‐field markers. This work paves the way for high‐fidelity subwavelength ultrasound imaging in heterogeneous environments, holding promising potential for advancements in biomedical imaging, nondestructive testing, and other related fields. [ABSTRACT FROM AUTHOR]