Broadband optical absorption based on single-sized metal-dielectric-metal plasmonic nanostructures with high-<i>ε</i>″ metals

Abstract

We propose a broadband, efficient, ultra-thin metal-insulator-metal (MIM) absorber with a simple single-sized disk configuration by utilizing metals with high imaginary part of permittivity (ε″). The physics behind this is that field dissipation is remarkably enhanced in MIM absorbers with high-ε″ metals, significantly extending the absorption bandwidths, which are conventionally limited by magnetic resonances of MIM absorbers with low-ε″ metals. The experimentally demonstrated MIM absorber based on tungsten with high-ε″ yields broadband absorption from visible to near-infrared range (400–1700 nm) with an average measured absorption of 84%. The ultra-thin and single-sized nanostructure with broadband efficient absorption facilitates the scalability to large-area photonic applications.