Mushroom-type HIS as a perfect absorber for two angles of incidence

In this work we show analytically and numerically that a mushroom-type high-impedance metasurface with loaded vias is capable to absorb perfectly electromagnetic TM-polarized plane waves for two angles of incidence (for normal incidence and for oblique incidence with a selected angle). Using the non-local homogenization model we demonstrated that this effect can be achieved due to the two types of losses: dielectric losses in the substrate of the metasurface and ohmic losses in lumped loads connecting vias to a ground plane. Moreover, we have shown that the angle of perfect absorption under oblique incidence can be tuned by varying the complex impedance of the loads.