Interference theory of metamaterial perfect absorbers

TL;DR

This paper presents a new interference-based theory for metamaterial perfect absorbers, challenging the traditional magnetic resonance explanation and clarifying the physics behind their impedance matching.

Contribution

It introduces a novel interference-based interpretation that explains the behavior of narrowband metamaterial absorbers without relying on magnetic resonances.

Findings

The two metal layers are linked by multiple reflections, not magnetic resonance.

Surface currents are out-of-phase due to superpositions from multiple reflections.

The theory explains all observed features of narrowband metamaterial absorbers.

Abstract

The impedance matching in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with a direct evidence from the anti-parallel directions of surface currents in the metal structures. Here we present a different theoretical interpretation based on interferences, which shows that the two layers of metal structure in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.