Numerical Investigation of Graphene and STO Based Tunable Terahertz Absorber with Switchable Bifunctionality of Broadband and Narrowband Absorption.

Yan Liu,Rui Huang,Zhengbiao Ouyang

doi:10.3390/nano11082044

Yan Liu, Rui Huang + Show 1 more

Open Access

https://doi.org/10.3390/nano11082044

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Journal: Nanomaterials	Publication Date: Aug 11, 2021
Citations: 13	License type: CC BY 4.0

Affiliation: Shenzhen University, Hanshan Normal University

Abstract

A graphene metamaterial and strontium titanate (STO)-based terahertz absorber with tunable and switchable bifunctionality has been numerically investigated in this work. Through electrically tuning the Fermi energy level of the cross-shaped graphene, the bandwidth of the proposed absorber varies continuously from 0.12 THz to 0.38 THz with the absorptance exceeding 90%, which indicates the functionality of broadband absorption. When the Fermi energy level of the cross-shaped graphene is 0 eV, the proposed absorber exhibits the other functionality of narrowband absorption owing to the thermal control of the relative permittivity of STO, and the rate of change of the center frequency is 50% ranging from 0.56 THz to 0.84 THz. The peak intensity of the narrowband absorption approximates to nearly 100% through adjusting the Fermi energy level of the graphene strips. The calculated results indicate that it is not sensitive to the polarization for wide incidence angles. The proposed absorber can realize tunable bifunctionality of broadband absorption with a tunable bandwidth and narrowband absorption with a tunable center frequency, which provides an alternative design opinion of the tunable terahertz devices with high performance for high-density integrated systems.

Highlights

Metamaterials, artificially engineered by subwavelength electromagnetic materials, show some optical properties that differ from natural materials
Fermi energy level of the cross-shaped graphene, a tunable broadband absorption of the bifunctional absorber can be obtained, and its bandwidth can realize a variation in the range of frequencies from 0.12 to 0.38 THz with excellent absorptance of over 90%
Ef1 varies from 0.4 eV to 0.8 eV, a broadband absorption is achieved, and its bandwidth

Summary

Introduction

Metamaterials, artificially engineered by subwavelength electromagnetic materials, show some optical properties that differ from natural materials. Tunable devices with multiple functionalities have been investigated including the bifunctional absorbers transforming from broadband absorption to narrowband absorption. Fermi energy level of the cross-shaped graphene, a tunable broadband absorption of the bifunctional absorber can be obtained, and its bandwidth can realize a variation in the range of frequencies from 0.12 to 0.38 THz with excellent absorptance of over 90%. When the Fermi energy level of the cross-shaped graphene is 0 eV, a narrowband absorption with tunable center frequencies can be achieved utilizing thermal control of the relative permittivity of STO. The bifunctional absorber inspires the design of dynamically tunable devices with multiple functionalities in the terahertz regime

Materials and Methods

Results and Discussion

Conclusions