Dark Superabsorbers with Dirac-delta-like superdirective radiation

TL;DR

This paper introduces the concept of dark superabsorbers, which are systems that maximize absorption while minimizing scattering, producing a Dirac-delta-like radiation pattern with potential applications in energy harvesting and imaging.

Contribution

It reveals the physical limitations and conditions for dark superabsorbers, including the role of angular momentum channels and the Dirac-delta-like far-field radiation pattern.

Findings

Existence of a maximum absorption cross section with minimal scattering under specific conditions.

Dark superabsorbers produce a needle-like Dirac-delta radiation pattern.

Complete Dirac-delta far-field radiation is theoretically excluded due to the Gibbs phenomenon.

Abstract

We theoretically and numerically reveal that under a given level of extinction cross section and with definite angular momentum channels dominant, there exists a physical limitation for absorption cross section being maximum and scattering cross section being minimum. In addition, any scattering systems operated at this condition would be accompanied by a needle Dirac-delta-like far-field radiation pattern, reducing to perturb the background field except in the forward direction. We therefore refer to this outcome as dark superabsorbers. Moreover, by considering the mathematical Gibbs phenomenon, we find that a completely equivalent Dirac-delta far-field radiation is excluded even we could properly design the scatterers operated at such conditions. We believe this finding has potential applications in design of dark energy harvesting, lower-visibility receivers, superdirective light-matter interaction, and Fresnel diffractive imaging.