Generalized Matching Theory for Perfect Transmission of Obliquely Incident Elastic Waves

We present a novel theory (generalized matching theory) to realize the perfect transmission of obliquely incident elastic waves across dissimilar media. Obliquely incident elastic waves inevitably generate both longitudinal and transverse waves at dissimilar solid-solid interfaces. Due to this intrinsic multimodality, the conventional impedance matching theory fails to achieve the perfect transmission of obliquely incident elastic waves. Here, we show that the perfect transmission across dissimilar media is possible if an anisotropic layer satisfying specific conditions is inserted between them. It is demonstrated that wave transmission from metal (aluminum) to plastic (Polyether ether ketone) plates can be enhanced from 20%-40% to nearly 100% with nearly zero reflection. Experimentally measured amplitudes of the transmitted longitudinal and transverse waves were found to be amplified by 2.59 and 4.55 times, respectively, when the anisotropic layer was inserted.