Freestanding dielectric nanohole array metasurface for mid-infrared wavelength applications

TL;DR

This paper presents the design and simulation of freestanding dielectric nanohole array metasurfaces in silicon, achieving 2π phase control and high transmission for mid-infrared applications, with optimized beam deflectors based on Kerker conditions.

Contribution

It introduces a novel design of freestanding silicon nanohole metasurfaces with tunable phase and high efficiency, advancing mid-infrared optical device capabilities.

Findings

Achieved 2π phase control and high forward transmission.

Identified Kerker conditions as key to high scattering efficiency.

Optimized beam deflector design for maximum transmission.

Abstract

We designed and simulated freestanding dielectric optical metasurfaces based on arrays of etched nanoholes in a silicon membrane. We showed $2\pi$ phase control and high forward transmission at mid-infrared wavelengths by tuning the dimensions of the holes. We also identified the mechanisms responsible for high forward scattering efficiency and showed that these conditions are connected with the well-known Kerker conditions already proposed for isolated scatterers. A beam deflector was designed and optimized through sequential particle swarm and gradient descent optimization to maximize transmission efficiency and reduce unwanted grating orders. Such freestanding silicon nanohole array metasurfaces are promising for the realization of silicon based mid-infrared optical elements.