Continuously tunable ultrasonic focusing by Moiré metalenses

Guo-Qiang Yuan; Xin-Rui Li; Xing-Feng Zhu; Jie Yao; Qi Wei; Da-Jian Wu

doi:10.1016/j.ultras.2024.107466

Continuously tunable ultrasonic focusing by Moiré metalenses

Ultrasonics. 2024 Sep 11:145:107466. doi: 10.1016/j.ultras.2024.107466. Online ahead of print.

Authors

Guo-Qiang Yuan¹, Xin-Rui Li², Xing-Feng Zhu³, Jie Yao⁴, Qi Wei⁴, Da-Jian Wu⁵

Affiliations

¹ Institute of Acoustics, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China.
² Institute of Acoustics, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China; Department of Architecture, College of Design and Environment, National University of Singapore, Singapore 117566, Singapore.
³ Institute of Acoustics, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China; MOE Key Laboratory of Modern Acoustics, School of Physics, Nanjing University, Nanjing 210093, China. Electronic address: zhuxingfeng@njnu.edu.cn.
⁴ Institute of Acoustics, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China; MOE Key Laboratory of Modern Acoustics, School of Physics, Nanjing University, Nanjing 210093, China.
⁵ Institute of Acoustics, School of Physics and Technology, Nanjing Normal University, Nanjing 210023, China. Electronic address: wudajian@njnu.edu.cn.

PMID: 39284242
DOI: 10.1016/j.ultras.2024.107466

Abstract

Tunable ultrasonic focusing holds great significance in both medicine and engineering. Recent advancements in metalenses have introduced approaches for tunable acoustic focusing, but their complex configurations and limited tuning range remain challenges. Here, acoustic Moiré metalenses (AMMs) are proposed to achieve continuously tunable ultrasonic focusing in water. Two cascading metasurfaces that can function as Moiré diffractive elements make up the AMM. By mutually rotating the metasurface, the focal point of the AMM can be continuously tuned in a large range. The focal length can be adjusted continuously from ∼14.3λ₀to ∼50λ₀for the axial focusing. We further show that the well-designed AMM can achieve the continuously tunable lateral focusing, with the deflection angle of the focal point being tunable between approximately -40^°,40^°. Both simulation and experimental results confirm the excellent tunable focusing performances of the AMMs. The proposed AMMs with continuously tunable focusing capability may have potential applications in ultrasonic imaging and ultrasound treatment.

Keywords: Continuously tunable; Metasurface; Moiré metalens; Ultrasonic focusing.