Ultrathin Perfect Absorbers for Normal Incident Waves Using Dirac Cone Metasurfaces With Critical External Coupling
Yuto Kato, Subaru Morita, H. Shiomi, Atsushi Sanada
Abstract
We propose an ultrathin perfect absorber for normal incident waves using a Dirac cone metasurface with the thickness of 1/38 free-space wavelength. First, we prepare Dirac cone metasurfaces consisting of periodic metallic chain patterns on a dielectric substrate having the Γ-point frequencies of approximately 30 GHz. The perfect absorber is designed by adjusting the external coupling of the Dirac cone metasurfaces with their chain densities. Based on the one-port resonator model, we clarify that the perfect absorber is realized at the critical coupling condition with identical internal and external Q-factors. We experimentally demonstrate a perfect absorption with the reflectance as small as -37 dB by the metasurface with the critical external coupling.