Perfect Absorption at the Ultimate Thickness Limit in Planar Films

TL;DR

This paper establishes fundamental thickness limits for perfect light absorption in planar films, providing a theoretical framework to guide ultra-thin, highly efficient nanophotonic devices.

Contribution

It introduces a novel analytical model linking absorber thickness to dielectric loss, enabling prediction and engineering of perfect absorption at minimal thicknesses.

Findings

Derived a simple relation between thickness and dielectric loss for perfect absorption.

Identified surprisingly low bounds on minimal thickness for total light absorption.

Provided a framework applicable to various resonant materials for ultra-thin absorber design.

Abstract

Reducing device volume is one of the key requirements for advanced nanophotonic technologies, however this demand is often at odds with designing highly absorbing elements which usually require sizeable thicknesses, such as for detector and sensor applications. Here we theoretically explore the thickness limitations of perfectly absorbing resonant systems and show surprisingly low bounds on minimal required thicknesses for total light absorption in thin planar films. We present a framework for understanding, predicting, and engineering topologically protected perfect absorption in a wide range of resonantly absorbing materials. The proposed analytical approach leads to a simple relation between a perfect absorbers thickness and dielectric function loss, which also serves as a guide for determining the absorption potential of existing and emerging materials at the ultimate thickness limit. The presented results offer new insights into the extremes of light-matter interaction and can facilitate the design of ultra-sensitive light absorbers for detector and sensor systems.