A Route to Unusually Broadband Absorption Spanning from Visible to Mid-Infrared

TL;DR

This paper proposes a simple, feasible design for an ultra-broadband absorber spanning visible to mid-infrared wavelengths, achieving over 90% absorption across a 2,800 nm range by embedding a thin manganese layer in a metal-insulator-metal structure.

Contribution

The study introduces a novel MIM-based structure with a 5 nm manganese layer that significantly broadens absorption bandwidth, combining plasmonic and non-plasmonic resonances for practical broadband absorption.

Findings

Achieves over 90% absorption from 478 to 3,278 nm

Bandwidth is over ten times wider with Mn layer

Simple fabrication with one lithography step

Abstract

In this paper, a route to ultra-broadband absorption is suggested and demonstrated by a feasible design. The high absorption regime (absorption above 90%) for the suggested structure ranges from visible to mid-infrared (MIR), i.e. for the wavelength from 478 to 3,278 nm that yields an ultra-wide bandwidth of 2,800 nm. The structure consists of a top-layer-patterned metal-insulator-metal (MIM) configuration, into the insulator layer of which, an ultra-thin 5 nm layer of Manganese (Mn) is embedded. The MIM configuration represents a Ti-Al2O3-Ti tri-layer. It is shown that, without the ultra-thin layer of Mn, the absorption bandwidth is reduced to 274 nm. Therefore, adding only a 5 nm layer of Mn leads to a more than tenfold increase in the width of the absorption band. It is explained in detail that the physical mechanism contributing to this ultra-broadband result is a combination of plasmonic and non-plasmonic resonance modes, along with the appropriate optical properties of Mn. This structure has the relative bandwidth (RBW) of 149%, while only one step of lithography is required for its fabrication, so it is relatively simple to fabricate. This makes it rather promising for practical applications.