Modelling of free-form conformal metasurfaces

Kedi Wu,Patrice Genevet,Qi Jie Wang,Philippe Coquet

doi:10.1038/s41467-018-05579-6

Abstract

Artificial electromagnetic surfaces, metasurfaces, control light in the desired manner through the introduction of abrupt changes of electromagnetic fields at interfaces. Current modelling of metasurfaces successfully exploits generalised sheet transition conditions (GSTCs), a set of boundary conditions that account for electric and magnetic metasurface-induced optical responses. GSTCs are powerful theoretical tools but they are not readily applicable for arbitrarily shaped metasurfaces. Accurate and computationally efficient algorithms capable of implementing artificial boundary conditions are highly desired for designing free-form photonic devices. To address this challenge, we propose a numerical method based on conformal boundary optics with a modified finite difference time-domain (FDTD) approach which accurately calculates the electromagnetic fields across conformal metasurfaces. Illustrative examples of curved meta-optics are presented, showing results in good agreement with theoretical predictions. This method can become a powerful tool for designing and predicting optical functionalities of conformal metasurfaces for new lightweight, flexible and wearable photonic devices.

Highlights

Metasurfaces, the two-dimensional (2D) counterparts of three-dimensional (3D) metamaterials, have attracted considerable research interest in recent years, regarding their intriguing ability to control every aspect of electromagnetic waves at the subwavelength scale[1]
The discontinuous variation of these electromagnetic fields across traditional planar metasurfaces can be modelled by considering specific boundary conditions called generalised sheet transition conditions (GSTCs)[8,27]
We propose an innovative algorithm to address free-form conformal metasurface designs. This algorithm relies on a revised finite-difference time-domain (FDTD) method, which has a great capacity for dealing with electromagnetic problems in complex geometries and inhomogeneous shapes

Summary

Introduction

Metasurfaces, the two-dimensional (2D) counterparts of three-dimensional (3D) metamaterials, have attracted considerable research interest in recent years, regarding their intriguing ability to control every aspect of electromagnetic waves at the subwavelength scale[1]. All of the published attempts to designing freeform metasurfaces have relied on the brute force approach to calculate the optical responses of a large library of individual scatterers, which are assembled side by side along non-planar devices to address the phase retardation between incident and refracted wavefronts[31].

Results

Conclusion