Ultrabroadband Near-perfect Anisotropic Metamaterial Absorber Based on a Curved Periodic W/TPX Stack

ABSTRACT A one-dimensional periodic microstructure was presented for an ultrabroadband near-perfect absorber for thermal radiation. The microstructure comprised a curved periodic stack of tungsten (15 nm) and polymethylpentene (TPX) (35 nm) with 20 layers deposited on a half-cylindrical cavity fabricated on a tungsten substrate. Visible to midinfrared regions (200 nm to 10.9 μm) allow an average measured light absorptivity of approximately 90% for transverse magnetic polarized waves at normal incidence; this property is insensitive to polar angle even when the incident angle is 80°. These superior performances were primarily attributed to intrinsic bandgap absorption in tungsten, excitation of SPPs at the air/W interface, and the resonance of the slow-light effect and its higher-order modes. Furthermore, the spectrum range of near-perfect absorption could be tuned by adjusting the center half-cylindrical shell radius, total pair number and dielectric permittivity. Moreover, the imperfection tolerance of the proposed system was studied by varying the filling ratio of metal in a periodic shell. This work may provide new guidelines for designing metamaterials absorbers that can obtain highly enhanced absorption over an ultrabroadband and in a wide range of angle of incidence.