Graphene-based dual-functional chiral metamirror composed of complementary 90° rotated U-shaped resonator arrays and its equivalent circuit model

Abstract

An equivalent circuit model (ECM) using a MATLAB code to analyze a tunable two-layered graphene-based chiral dual-function metamirror, is proposed in this work. The investigated metastructure is composed of complementary U-shaped graphene resonator arrays in the terahertz (THz) region. The ECM analysis could be used for any two-layered chiral metastructure for any frequencies, containing resonators with a thickness less than λ/50. The characteristics of the proposed tunable metamirror were analyzed numerically using the finite element method (FEM) in CST Software to verify the ECM analysis. The proposed metamirror can be used in polarization-sensitive devices in the THz region with simpler biasing without a need for ion gels or similar. It works as a broadband TE and multiband (four bands) TM mirror in the 0.3–4.5 THz bandwidth with a strong linear dichroism (LD) response (up to 96%). The designed mirror is a dynamically tunable, dual-functional structure, requiring only 90° rotation of the incident electromagnetic fields to switch between broadband and multiband spectral behavior making it a promising candidate for future THz intelligent systems. The proposed ECM is in agreement with the FEM results. The ECM analysis provides a simple, fast, and effective way to understand the metamirror’s behavior and guides for the design and analysis of graphene-based chiral metastructures in the THz region.

Graphene-Based Multiband Chiral Metamaterial Absorbers Comprised of Square Split-Ring Resonator Arrays With Different Numbers of Gaps, and Their Equivalent Circuit Model

“…Graphene based unit cell resonators of chiral metamaterials have been designed and developed recently to produce tunable chirality responses [2][3][4][5][6][7][8]. These metamaterials have a chirality response of up to 96%.…”

“…Our earlier paper [6] reported a multi-band graphene-based chiral metamaterial absorber containing a single-layer Ushaped resonator array with the LD chirality response reaching 94%. While the other work [7] introduced a dualfunctional graphene-based chiral metamirror containing twolayered complementary 90° rotated U-shaped resonator arrays with an LD response reaching 96%. In this work, we propose multi-band graphene-based chiral metamaterial absorbers containing single-layer square split-ring resonator arrays with different numbers of gaps.…”

“…Compared to the earlier published paper [6], were carried out simulations for a similar one gap structure but in a different frequency range (1-5.5 THz). Compared to the paper [7], simulation and circuit modeling procedures of this work are assumed to be less resource demanding as the proposed structure contains only a simple single resonator layer and dielectric.…”

“…The gap of the structure is modeled by a parallel capacitor and the ECM of the structure containing ion gel/graphene/dielectric/gold layers is developed by use of the ABCD matrix. In the case of the paper [7], we used equivalent conductivity relations to obtain the conductive characteristics of graphene patterns. Then the transfer matrix elements were determined for the structure to obtain the reflection characteristics of the metastructure, containing graphene/dielectric/graphene/ dielectric/gold layers.…”

“…Proposed tunable chiral absorbers could utilized in applications such as enhancement of chirality responses for chiral biomolecules like DNA and amino acids since the natural biomolecules have weak chirality responses [7], polarization transformers, stealth technology, thermal bolometers [9], wavelength-selective absorption filters, hotelectron collection devices [10], chiral imaging to achieve distinct displayed images by switching the polarization of the incident wave [14] in the THz range.…”