Anisotropic Virtual Gain and Large Tuning of Particles' Scattering by Complex-Frequency Excitations

TL;DR

This paper introduces a novel method to actively control particle scattering by using anisotropic virtual gain, enabling large tuning of scattering direction and magnitude through complex-frequency excitation without physical medium reconfiguration.

Contribution

The study presents the concept of anisotropic virtual gain and oblique Kerker effect, allowing tuning of scattering properties via excitation shape rather than medium tuning.

Findings

Enables directional super-scattering at oblique angles.

Achieves large scattering tuning by changing excitation envelope.

Analytical multipolar decomposition matches full-wave simulations.

Abstract

Active tuning of the scattering of particles and metasurfaces is a highly sought-after property for a host of electromagnetic and photonic applications, but it normally requires challenging-to-control tunable (reconfigurable) or active (gain) media. Here, we introduce the concepts of anisotropic virtual gain and oblique Kerker effect, where a completely lossy anisotropic medium behaves exactly as its anisotropic gain counterpart upon excitation by a synthetic complex-frequency wave. The strategy allows one to largely tune the magnitude and angle of a particle's scattering simply by changing the shape (envelope) of the incoming radiation, rather than by an involved medium-tuning mechanism. The so-attained anisotropic virtual gain enables directional super-scattering at an oblique direction with fine-management of the scattering angle. Our study, opening a unique light-management method, is based on analytical techniques that allow multipolar decomposition of the scattered field, and is found, throughout, to be in excellent agreement with full-wave simulations.