Ultra-Broadband Polarization- and Angle-Insensitive Perfect Meta-Absorber for Energy Harvesting and Thermal Infrared Detection

Abstract

Broadband plasmonic metamaterial absorbers are highly sought after for their use in energy harvesting applications. Here, we theoretically demonstrate a nanophotonic perfect meta-absorber comprised of a two-dimensional (2D) array of pyramidal multi-layered metal-dielectric (MD) structures. Each multi-layered structure has 20 pairs of alternating MD layers comprising titanium nitride (TiN) and silicon dioxide (SiO₂), with an optically-thick TiN metal layer as back reflector. We theoretically show an exceptional average absorbance of 99.17% at normal incidence spanning ultra-broadband wavelength range of 0.3–5 μm, with peak absorbance of 99.99% at 1.28 μm wavelength. The proposed nanophotonic meta-absorber has an average absorbance of at least 94% for up to 60° of oblique incidence for random polarization. Thus, our proposed design is both angle-insensitive and polarization-independent. Our effective medium theory-based theoretical modeling comprehensively verifies the results obtained from full-wave simulations. Furthermore, the calculated figure-of-merit for the proposed meta-absorber suggests that it can outperform some broadband absorbers recently reported in the literature. Thus, the suggested meta-absorber has potential applications in energy harvesting and thermal infrared detection.