Metallic rugate structures for perfect absorbers in visible and near-infrared regions

TL;DR

This paper explores metallic rugate structures with sinusoidal porosity profiles for achieving perfect and broadband absorption in the visible and near-infrared spectrum, adaptable to various polarizations and incident angles.

Contribution

It introduces a theoretical model of nanoporous metallic rugate structures with sinusoidal porosity for perfect absorption, including multi-periodic designs for enhanced spectral performance.

Findings

Achieves perfect absorption in visible and near-infrared regions.

Supports high absorption for multiple polarizations and incident angles.

Enables multi-peak absorption through multi-periodic structures.

Abstract

Metallic rugate structures are theoretically investigated for achieving perfect absorption in the visible and near-infrared regions. Our model builds on nanoporous metal films whose porosity (volume fraction of voids) follows a sine-wave along the film thickness. By setting the initial phase of porosity at the top surface as 0, perfect absorption is obtained. The impacts of various structural parameters on the characteristic absorption behaviors are studied. Furthermore, multiple peaks or bands with high-absorption can be achieved by integrating several periodicities in one structure. The rugate absorbers show perfect or near-perfect absorption for TE and TM polarizations and large incident angles.