Broadband perfect absorption of ultrathin conductive films with coherent illumination:Superabsorption of microwave radiation

TL;DR

This paper demonstrates that coherent illumination of ultrathin conductive films can achieve broadband perfect microwave absorption, overcoming traditional 50% limits and enabling total wave absorption across a wide frequency spectrum.

Contribution

It introduces a novel method of using coherent dual-beam illumination to achieve 100% broadband microwave absorption on ultrathin conductive films, breaking previous limitations.

Findings

Achieves near 200% bandwidth for microwave absorption.

Demonstrates total absorption on films thinner than λ/10,000.

Breaks the 50% absorption limit with coherent illumination.

Abstract

Absorption of microwave by metallic conductors is exclusively inefficient, though being natively broadband, due to the huge impedance mismatch between metal and free space. Reducing the thickness to ultrathin conductive film may improve the absorbing efficiency, but is still bounded by a maximal 50% limit induced by the field continuity. Here, we show that broadband perfect (100%) absorption of microwave can be realized on a single layer of ultrathin conductive film when it is illuminated coherently by two oppositely incident beams. Such an effect of breaking the 50% limit maintains the intrinsic broadband feature from the free carrier dissipation, and is frequency-independent in an ultrawide spectrum, ranging typically from kilohertz to gigahertz and exhibiting an unprecedented bandwidth close to 200%. In particular, it occurs on extremely subwavelength scales, ~{\lambda}/10000 or even thinner, which is the film thickness. Our work proposes a way to achieve total electromagnetic wave absorption in a broadband spectrum of radio waves and microwaves with a simple conductive film.