Phase-controllable elastic impedance matching via Willis metamaterials
Phys. Rev. Applied 26, 014098 – Published 31 July, 2026
DOI: https://doi.org/10.1103/6622-xpm5
Abstract
The conventional impedance matching based on Fabry-Perot resonance has been widely used to overcome impedance mismatch. However, the phase of transmitted wave in impedance matching system is fixed to certain value. This constraint in phase limits the applications of wave manipulation, which requires spatial phase distribution. In this paper, we find out that Willis metamaterials composed of geometrically asymmetric unit cell can achieve impedance matching with tunable phase over a geometry-dependent range. By exploiting the complex-valued impedance arising from Willis coupling, we fundamentally alter the classical Fabry-Perot resonance conditions to achieve full transmission. This mechanism enables independent control of the phase of transmitted waves. We validate these theoretical predictions through numerical simulations and experimental demonstrations with continuum aluminum structures. Our findings establish a new platform using Willis metamaterials for versatile wave manipulation devices, overcoming long-standing design constraints.
