Ultra-Broadband Absorber Based on Metal-Insulator-Metal Four-Headed Arrow Nanostructure

We propose an ultra-broadband metamaterial absorber composed of a four-headed arrow-shaped top layer and titanium-bottom film spaced by a dielectric layer. The absorber attains an average absorption of 95.21% ranging from 300 to 2000 nm, and the peak absorptivity reaches up to 99.9%. The synergy of surface plasmon resonances, cavity modes, and lightning-rod effects lead to the ultra-broadband perfect absorption. We also demonstrate the proposed absorber is insensitive for both transverse electric and transverse magnetic polarization and can retain 90% absorption at a larger incident angle. The proposed ultra-broadband absorber holds promising potential in solar cells, optical imaging, polarization detectors, and other large-area applications.