High-Throughput Superresolved Focal Imaging Based on a Phase-Modulated Acoustic Superoscillatory Lens

Abstract

Breaking the Abbe-Rayleigh diffraction limit and realizing acoustic superdiffraction focusing and imaging is of great significance in acoustic science and engineering. While a conventional focusing lens cannot even reach the Abbe-Rayleigh resolution limit due to the cutoff of spatial-frequency components of the regular lens. Superoscillation technology paves a way to generate superdiffraction for acoustic superresolution imaging. However, high-transmission superresolution is still a challenge issue in the imaging field of acoustics. Here, we propose a high-throughput phase-modulated acoustic-superoscillatory-lens (ASOL) focal-imaging technology. The ASOL is made up of many subwavelength spiral metamaterial elements for superimposing different spatial-frequency components to generate a superdiffraction focal spot. For proof of concept, the design and fabrication of the phase-modulated ASOL, a 0.326\ensuremath{\lambda} focal spot with a 0.9 transmission coefficient, is achieved through both simulation and experiment. Moreover, a superresolution focal-imaging experiment is successfully demonstrated by the Chinese traditional window-grille structure with a slit width of 0.33\ensuremath{\lambda}. It verifies that the proposed ASOL has the great technical potential to improve acoustic-focal-imaging resolution. The proposed method also opens up opportunities for developing high-throughput acoustic superresolution imaging, and it will reduce the reflection effect and improve the signal-to-noise ratio. The proposed ASOL has significant potential applications in underwater sonar scanning, acoustic diagnosis, and acoustic imaging technology.