Elastic Metagratings with Simultaneous Modulation of Reflected and Transmitted Waves

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.