# Metasurface engineering through bound states in the continuum

## TL;DR

This paper explores how symmetry-breaking in metasurfaces can control high-Q resonances from bound states in the continuum, enabling tailored wavefront manipulation with experimental demonstrations of magnetic and toroidal dipole responses.

## Contribution

It introduces a method to manipulate Fano resonances in metasurfaces via transverse symmetry breaking, controlling the number, frequency, and type of bound states in the continuum.

## Key findings

- Controlled high-Q resonances through symmetry breaking.
- Experimental realization of magnetic and toroidal dipole metasurfaces.
- Demonstrated tunability of Fano resonances in metasurfaces.

## Abstract

Metasurfaces have attracted a lot of attention in recent years due to novel ways they provide for the efficient wavefront control and engineering of the resonant transmission. We discuss an approach allowing effectively control appearance of the sharp Fano resonances in metasurfaces associated with the {\it bound states in the continuum}. We demonstrate that by breaking the symmetry transversely, in the direction perpendicular to a metasurface with a complex unit cell, we can control the number, frequency, and type of high-$Q$ resonances originating from bound states in the continuum. As example, we demonstrate experimentally the metasurfaces with magnetic dipole and toroidal dipole responses governed by the physics of multipolar bound states.