Ultrabroadband Nanostructured Metamaterial Absorber for Visible and Short-Infrared Spectrum

This research investigates the design of a nanostructured metamaterial absorber, featuring a core composition of nickel (Ni) metallic patch surrounded by an inductive grid. The proposed Ni-based nano-absorber exhibits a remarkable absorption bandwidth, spanning both visible and short-infrared wavelengths, with an impressive average absorption efficiency of 90% from 400 to 2000 nm. This study comprehensively examines the absorption characteristics of the nano-absorber across a range of incident angles and polarization states of optical light. Notably, the absorber demonstrates a polarization-insensitive response due to the inherent four-fold symmetry within its nanoresonator design and gives a sizeable absorption for various incident angles. Furthermore, the paper also investigates the surface electric field for a deeper understanding of its performance. Additionally, an equivalent circuit model has been developed for the proposed nanostructured absorber, and a comparison between the simulated and analytical absorption shows a close agreement between them. The simple and easily fabricable design of this absorber makes it a promising candidate for diverse applications, encompassing energy harvesting, solar cells, photodetectors, etc. Furthermore, the straightforward and versatile geometry of the proposed nano-absorber can be readily adapted for use in different operating frequency spectra, including microwave and terahertz ranges.