Elastic Metagratings with Simultaneous Modulation of Reflected and Transmitted Waves

Abstract

Elastic metagratings enabling independent and complete control of both reflection and transmission of bulk longitudinal and transverse waves are highly desired in application scenarios such as non-destructive assessment and structural health monitoring. In this work, we propose a kind of simply structured metagrating composed only of elliptical hollow cylinders carved periodically in a steel background. By utilizing the grating diffraction theory and genetic algorithm, we endow these metagratings with the attractive functionality of simultaneous and high-efficiency modulation of every reflection and transmission channel of both longitudinal and transverse waves. Interesting wave-front manipulation effects including pure mode conversion and anomalous deflection along the desired direction are clearly demonstrated through full-wave numerical simulations. Due to its subwavelength thickness and high manipulation efficiency, the proposed metagrating is expected to be useful in the design of multifunctional elastic planar devices.

Elastic metamaterials for guided waves: from fundamentals to applications

“…Despite successful applications of metasurfaces based on the generalized Snell's law, they can generate parasitic wave modes because the generalized Snell's law ignores higherorder diffraction wave modes. To avoid the formation of undesirable scattered fields, thereby preventing energy from leaking into the scattered waves, elastic metagratings [197][198][199][200][201] based on the diffraction theory have been investigated. The diffraction theory [202] can be written as…”