Spatial Symmetries in Multipolar Metasurfaces: From Asymmetric Angular Transmittance to Multipolar Extrinsic Chirality

TL;DR

This paper introduces a symmetry-based framework to analyze metasurfaces, enabling quick identification of properties like chirality and asymmetric transmission without complex calculations.

Contribution

It presents a novel, accessible method linking spatial symmetries to material parameters and scattering, simplifying metasurface analysis and revealing multipolar extrinsic chirality.

Findings

Demonstrates the existence of multipolar extrinsic chirality in achiral structures

Provides a symmetry-based approach that avoids complex group theory

Enables efficient determination of metasurface scattering properties

Abstract

We propose a framework that connects the spatial symmetries of a metasurface to its material parameter tensors and its scattering matrix. This provides a simple yet effective way to effortlessly determine properties of a metasurface scattering response, such as chirality or asymmetric transmission, and which of its effective material parameters should be taken into account in the prospect of a homogenization procedure. In contrast to existing techniques, this approach does not require any a priori knowledge of group theory or complicated numerical simulation schemes, hence making it fast, easy to use and accessible. Its working principle consists in recursively solving symmetry-invariance conditions that apply to dipolar and quadrupolar material parameters, which include nonlocal interactions, as well as the metasurface scattering matrix. The overall process thus only requires listing the spatial symmetries of the metasurface. Using the proposed framework, we demonstrate the existence of multipolar extrinsic chirality, which is a form of chiral response that is achieved in geometrically achiral structures sensitive to field gradients even at normal incidence.