Polarization-insensitive ultra-wideband metamaterial absorber comprising different forms of ZrN structures at the metasurface

Abstract

Ultra-wideband metamaterial absorber comprising zirconium nitride (ZrN)-based metasurface was investigated. In particular, the metasurface had three different kinds of resonating element patterns (composed of ZrN), namely the concentric annular square, circular and triangular air gaps of different samples of ZrN, as distinguished by the nitrogen content of the medium (i.e., ZrN). Spectral performance of metamaterials was evaluated in terms of absorbance, and it was found that the metasurface structure with annular circular resonating elements provides the best performance owing to high absorbance with relatively stable wideband feature. The performance of the proposed structures was investigated under varying parametric situations considering the incidence excitations with the transverse electric (TE-) and transverse magnetic (TM-) conditions, and also, the normal and oblique incidence of waves. The nearly-perfect absorption along with the ultra-wideband property of the structure were shown. Apart from this, it also exhibits the polarization-insensitive characteristic regardless of the polarization state as well as polarization angle of the incidence waves. Such a kind of absorber would be useful for antireflection coating and solar energy harvesting applications in a wide spectral range from the visible to far-red regimes of wavelength.