Broadband Infrared Absorption Features of Metasurfaces Constructed with a Titanium–Dielectric–Titanium Array Architecture

This study proposes an effective method for realizing broadband-infrared (IR)-equivalent absorption using a metasurface constructed by shaping a metal-insulator-metal structure leading to a semi-opened nanocavity. The metasurface architecture is formed according to an optimized structural configuration and mature micro-nano-fabrication flow. Both the surface travelling and localized resonant wavefield accumulation excited by incident lightwaves in a broad wavelength range of 1-14 μm can be efficiently manipulated based on a dipole molecule antenna responding mechanism. An electromagnetic wavefield shielding effect within the semi-opened nanocavity and the standing-wave formation around the metasurface near-field based on an arrayed titanium-dielectric-titanium structure are examined in detail. The measured IR spectral absorption characteristics reveal that the metasurfaces based on an arrayed top titanium cap with the featured dimensions of 2.0 μm and 2.4 μm can be used to achieve an average equivalent IR absorptivity higher than 80% and 82%, respectively, across a broad wavelength range of 1.29-14 μm, which covers the traditional short-, medium- and long-wave IR bands.