Dynamically Switchable Polarization-Independent Triple-Band Perfect Metamaterial Absorber Using a Phase-Change Material in the Mid-Infrared (MIR) Region.

Dongdong Xu,Fenping Cui,Gaige Zheng

doi:10.3390/mi12050548

Dongdong Xu, Fenping Cui + Show 1 more

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https://doi.org/10.3390/mi12050548

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Abstract

A tunable metamaterial absorber (MMA) by reversible phase transitions in a mid-infrared regime is theoretically investigated. The absorber is composed of a molybdenum (Mo)-germanium-antimony-tellurium (Ge2Sb2Te5, GST)-Mo nanodisk structure superimposed on the GST-Al2O3 (aluminum oxide)-Mo film. Studies have shown that the combination of the inlaid metal-medium dielectric waveguide mode and the resonant cavity mode and the excitation of the propagating surface plasmon mode are the main reasons for the formation of the triple-band high absorption. Additionally, through the reversible phase change, the transition from high absorption to high reflection in the mid-infrared region is realized. The symmetry of the absorber eliminates the polarization dependence, and the near unity absorption efficiency can be maintained by incidence angles up to 60°. The presented method will enhance the functionality of the absorber and has the potential for the applications that require active control over light absorption.

Highlights

Ge2 Sb2 Te5 (GST) is a phase-change material in which an increase in temperature within the material under the direct action of an external electric field or thermal stimulus leads to a transformation of the internal structure from the amorphous (AGST) state to the crystalline (CGST) state, accompanied by a series of changes in the physical properties of the material, such as the refractive index and electrical conductivity [32,33]
Mo is used as a retro-reflector to avoid incident light passing through the metal film, reducing the fugitive work rate and increasing the absorbance to close to unity
For GST films, the dielectric constant changes dramatically once the phase change is triggered by a thermal field

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Ge2 Sb2 Te5 (GST) is a phase-change material in which an increase in temperature within the material under the direct action of an external electric field or thermal stimulus leads to a transformation of the internal structure from the amorphous (AGST) state to the crystalline (CGST) state, accompanied by a series of changes in the physical properties of the material, such as the refractive index and electrical conductivity [32,33]. The formation of three resonant absorption peaks in the MIR range of 8–20 μm can be observed in the crystalline phase. The absorber has good triple frequency absorption performance, good operating angle polarization tolerance, and dynamic tunability advantages, which may be beneficial for a variety of MIR applications

Model and Methods

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