Design of a Perfect Absorber for Normal Incident Waves Using Dirac Cone Metasurface with Anchor Shaped Unit Cells

We propose a thin perfect absorber for normal incident waves using Dirac cone metasurface with anchor shaped unit cells. The coupling between an incident wave and guided waves is quantitatively characterized by the external Q value and it is shown that the coupling can be controlled by the density of the lines in the metasurface by full-wave simulations. It is also shown that the perfect absorption is originated from the fact that the incident wave and the guided wave in the metasurface are critically coupled with an identical internal and external Q values. The maximum absorption reaches 37.0 dB even by the structure with the thickness of λ/40.