Elastic Metagratings with Simultaneous Highly Efficient Control over Longitudinal and Transverse Waves for Multiple Functionalities

Elastic metagratings that can efficiently manipulate the propagation of bulk longitudinal and transverse waves are highly desired in various applications, such as geological exploration and nondestructive detection. Here, a class of elastic metagratings consisting of a one-dimensional array of elliptical hollow cylinders carved in a steel background is proposed and studied. With the help of elastic-wave-diffraction analysis and a genetic-algorithm-based optimization approach, these intelligently designed metagratings can reflect longitudinal and transverse waves in a highly efficient and spatially separated way. Various wave-front-manipulation functionalities, such as specular reflection for longitudinal waves and anomalous reflection for transverse waves, can be simultaneously achieved with an almost perfect efficiency. Interestingly, different functionalities over both longitudinal and transverse waves can be realized by using the same cylinders with different rotation angles. Due to the nonresonant characteristics, the exhibited functionality shows robustness over both working frequencies and unit-cell configurations, which are beneficial for practical applications.