Multifrequency superscattering from subwavelength hyperbolic structures

TL;DR

This paper demonstrates the theoretical possibility of achieving superscattering at multiple frequencies using subwavelength hyperbolic structures, including natural materials like hexagonal boron nitride, with high tolerance to losses.

Contribution

It introduces the concept of multifrequency superscattering in hyperbolic structures, revealing the mechanism and showing its robustness against material losses and structural variations.

Findings

Multifrequency superscattering is achievable in hyperbolic structures.

The mechanism relies on multimode resonances due to phonon-polaritons.

High tolerance to material losses and structural variations is demonstrated.

Abstract

Superscattering, i.e., a phenomenon of the scattering cross section from a subwavelength object exceeding the single-channel limit, has important prospects in enhanced sensing/spectroscopy, solar cells, and biomedical imaging. Superscattering can be typically constructed only at a single frequency regime, and depends critically on the inescapable material losses. Under such realistic conditions, superscattering has not been predicted nor observed to exist simultaneously at multiple frequency regimes. Here we introduce multifrequency superscattering in a subwavelength hyperbolic structure, which can be made from artificial metamaterials or from naturally-existing materials, such as hexagonal boron nitride (BN), and show the advantage of such hyperbolic materials for reducing structural complexity. The underlying mechanism is revealed to be the multimode resonances at multiple frequency regimes as appear in BN due to the peculiar dispersion of phonon-polaritons. Importantly, the multifrequency superscattering has a high tolerance to material losses and some structural variations, bringing the concept of multifrequency superscattering closer to useful and realistic conditions.