Broadband, Polarization-insensitive and Wide-angle Optical Absorber based on Fractal Plasmonics

摘要

In this paper, a plasmonic absorber consisting of a metal-dielectric-metalstack with a top layer of Sierpinski nanocarpet is theoretically investigated.Such compact absorber depicts broadband angle-independent behavior over a wideoptical wavelength range ($400-700$ nm) and a broad range of angles of lightincidence ($0-80^{\circ}$). Including several feature sizes, such fractal-likestructure shows widely strong extinction ($85-99$%) response for eithertransverse electric or magnetic polarization states under normal incidence.Underlying mechanisms of absorbance due to excited surface plasmon modes aswell as electric/magnetic dipole resonances are well revealed by investigatingelectric field, magnetic field and current distributions. The proposed absorberopens a path to realize high-performance ultrathin light trapping devices.