Bianisotropy and magnetism in plasmonic gratings

TL;DR

This paper demonstrates a simple ultrathin plasmonic gold grating design that exhibits bianisotropy, magneto-electric coupling, and asymmetric optical responses at visible wavelengths, advancing metasurface control.

Contribution

It introduces a novel, simple design for bianisotropic metasurfaces at visible wavelengths, with experimental validation and analysis of asymmetric optical behavior.

Findings

The device exhibits magneto-electric coupling and asymmetric reflection and absorption.

Spectral analysis and parameter retrieval confirm strong coupling and asymmetry.

Both asymmetry and strong coupling are essential for asymmetric optical behavior.

Abstract

We present a simple design to achieve bianisotropy at visible wavelengths: an ultrathin plasmonic grating made of a gold grating covered by a thin flat layer of gold. We show experimentally and through simulations that the grating exhibits magneto-electric coupling and features asymmetric reflection and absorption, all that with a device thickness of a tenth of the operating wavelength. We compared the spectral results and retrieved the effective material parameters of different polarizations and devices. We show that both asymmetry and strong coupling between the incoming light and the optically interacting surfaces are required for obtaining asymmetric optical behavior in metasurfaces.