Wide-band and wide-angle, visible- and near-infrared metamaterial-based absorber made of nanoholed tungsten thin film

Abstract

In this paper, the absorptivity of a tungsten ($W$W) based metamaterial absorber has been studied. The paper revolves around the spectral characteristics of the nano-holed $W$W film coated over silicon oxide (SiO${_2}$2) substrate. The anisotropic effective permittivity of the nanoholed W film has been deduced by employing the effective medium theory. The light-plasmon coupling at $W$W-$SiO_{2}$SiO2 interface has been investigated by the eigenvalue equation. The effect of the nanoholed radii on coupling and absorptivity has been analyzed. As such, absorption features of the absorber have been studied in the visible and near-infrared (NIR) regimes by finite difference time domain(FDTD) simulation under the excitation of fundamental transverse electric(TE)- and transverse magnetic (TM)-mode. It has been observed that absorptivity can be altered by tailoring the holes radii of tungsten nanolayer. Further, the effects of the incidence angle of the light on the absorptivity have been studied. Observations reveal that absorptivity depends on the nanohole radius of $W$W, and angle of incidence of excited light. Also, wideband absorptivity has been attained using $W$W thin film. Such an absorber would be useful for solar cell, solar heating and integrated optics related applications.