Figure 1

(a) Design and dimensions of the metasurface discussed in this study. (b) The dispersion curves of an elastic halfspace for ultrasonic frequencies measured at the top surface featuring surface Rayleigh (red) and shear (green) S-waves. The P-wave dispersion is marked with a dashed grey line. The introduction on the surface of local vertical resonators, (shown in the inset with the corresponding modal deformation), modifies the dispersion properties introducing a hybrid curve (blue) characterised by a bandgap (yellow area) bounded from below by an ultra slow mode and from above by a fast wave (pink diamonds). The S-wave serves as the light line, limiting the maximum speed of this system. (c) When Rayleigh waves approach an array of resonators of decreasing height (increasing resonance frequency), they are smoothly converted into S-waves. (d) Conversely, when the resonators are of increasing height, waves are spatially segregated, amplified and reflected.