Mode conversions for transmitted and reflected elastic waves by ultrathin elastic metamaterials plate with anisotropic resonances


 In this work, we study the conversions between longitudinal and transverse modes by one layer of oblique anisotropic dipolar resonators, whose size can be orders smaller than the wavelength. The mode conversions are found for both transmitted and reflected waves by such small resonators with a normal incidence. A mass-spring model is proposed to depict analytically the mode conversion, giving simplified analytical expressions for the conversion rates. The reflected conversion will gradually increase to the maximum while the solid material behind resonators becomes soft, or vice versa. It may provide theoretical guidance for practical application.