Large‐Area, Ultrathin Metasurface Exhibiting Strong Unpolarized Ultrabroadband Absorption

Abstract Large‐area, ultrathin devices with strong ultrabroadband absorption and high angular tolerance are in demand for applications such as ultraviolet protection, energy harvesting, photodetectors, and thermal imaging technology. Although there have been considerable efforts to design and fabricate these devices, the simultaneous realization of all desired properties has not been achieved. A 330 nm thick metasurface with an area of 3 cm² is experimentally developed, which incorporates dielectric cylinder arrays, a titanium nitride (TiN) layer, and silicon nitride (SiN_x) layers. The developed metasurface absorbs ≈87% of ultrabroadband light in the range of 250–2250 nm, which covers almost the entire solar spectrum, and has a low hemispherical thermal emittance of ≈29% in the long‐infrared range (5–13 µm). Moreover, the structure exhibits strong ultrabroadband absorption over a wide range of incident angles (82% at 60°). In addition, due to the high temperature resistance of TiN and its excellent spectral and angular performance, the device made from this material is ideal for solar‐thermal applications.