An ultra-broadband perfect absorber for visible to near-infrared light utilizing a metamaterial nanostructure is theoretically proposed and numerically analyzed. The absorber consists of a square and plus shape layer of Ti-Al2O3 (top layer) and a thin layer of Cr located on a SiO2 layer over a TiN substrate. By ameliorating the dimensions of the design, an average absorption of 95.4% is attained for wavelengths from 400 to 1800 nm, with a peak absorption of about 100%. Also, the bandwidths corresponding to the absorption above 90% and 99% are 1317 and 773 nm, respectively. The cooperative effects of the corresponding localized plasmonic resonances and the propagating surface plasmons of Ti resonators subsidize to the absorption response. Furthermore, the spectral response of the proposed nanostructure is insensitive to incident angle and independent of polarization angle. The proposed absorber has application prospects in photovoltaic devices, solar energy harvesting, and light trapping.

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