Triangular metallic ring-shaped broadband polarization-insensitive and wide-angle metamaterial absorber for the visible regime

The inherent bandwidth limitations make it quite challenging to achieve the wideband response of metamaterial absorbers. In this paper, a metamaterial absorber based on triangular metallic rings has been proposed to attain wideband absorption (>90%) in the wavelength span of 400-750 nm. The absorber is constituted of periodically placed unit cells, where each unit cell contains three concentric triangular chromium metal rings. The absorption of the design remains stable (above 70%) over a wide range of incidence obliquity (0°-60°) under transverse electric (TE) and transverse magnetic (TM) polarization. Further, the absorber shows polarization-insensitive behavior over different polarization states. The low-cost and thermally endurable chromium metal, wide absorption, and wide-angle stability make the proposed absorber a suitable candidate for applications like solar energy harvesting, solar detectors, solar thermal photovoltaics, and photonic devices.