Non-resonant metasurface for broadband elastic wave mode splitting

Complex polarizations of elastic waves allow mode conversions between two solids, making wave mode separation extremely difficult even for a narrow frequency range with resonant metamaterials. In this Letter, a non-resonant elastic metasurface design is proposed to achieve a perfect splitting of longitudinal and shear waves in space. The key to this broadband design is a singly polarized solid with engineered static elastic tensor, which provides a tool to tune the polarization through non-resonant microstructure design. Both full-wave simulations and experiments are conducted to validate the mode splitting function of the designed metasurface. Potential applications such as elastic wave shifting and selective wave mode focusing are also demonstrated. This research provides an alternative route to design broadband and compact metasurfaces for elastic wave communications, biomedical diagnosis, and wave-based damage evaluations.