Wideband Antireflection Coating Using Metamaterials

TL;DR

This paper introduces a metamaterial-based wideband antireflection coating design that achieves high fractional bandwidth and polarization insensitivity, with potential applications across a broad frequency spectrum.

Contribution

It presents a novel metamaterial structure with adjustable impedance and multilayer matching to significantly enhance bandwidth of antireflection coatings.

Findings

Achieves 56% fractional bandwidth with 10% reflectance

Bandwidth increases to 107% using multilayer Chebyshev transformer

Design is polarization-insensitive at normal incidence

Abstract

In this paper, we propose a new approach for realizing antireflection coating using metamaterials. In this approach, a subwavelength array of metallic pillars (with square cross-section) is used for implementing antireflection coating. The effective impedance of the array can be duly adjusted by the size and distance of pillars. Therefore, we design the effective impedance of the antireflection coating to be the geometrical mean of the upper and lower mediums impedance and we choose its height to be a quarter of operating wavelength. Consequently, the reflection vanishes at the desired frequency and fractional bandwidth of 56% is achieved with a criterion of 10% reflectance (the refractive index of the substrate is assumed to be 4). The proposed structure is symmetric in both directions. So, it is not sensitive to the polarization of the incident wave at normal incidence. Furthermore, we show that using the multilayer Chebyshev matching transformer of transmission line theory increases the bandwidth of the antireflection up to 107% at the expense of pass-band ripples. This structure can be used from very low frequencies up to infrared regime by appropriate scaling.