Abstract-Terahertz bifunctional absorber based on a graphene-spacer-vanadium dioxide-spacer-metal configuration

Man Zhang and Zhengyong Song

3D diagram of the proposed bifunctional metamaterial absorber.

Simulated electric field distributions in the XOY plane at the peak frequencies of 1.25 THz (a) and 2.13 THz (b) for broadband absorption, and simulated magnetic field distribution in the XOZ plane at 1.37 THz (c) for narrowband absorption.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-8-11780

A terahertz bifunctional absorber is presented with broadband and narrowband absorbing properties in a graphene-spacer-vanadium dioxide-spacer-metal configuration. Carrier relaxation time of graphene τ = 1.0ps (τ = 0.1ps) is chosen for narrowband (broadband) absorption. When vanadium dioxide is in the conducting state, the design behaves as a narrowband absorber, and it is composed of a square-shaped graphene, topas spacer, and metallic vanadium dioxide film. There is an absorption band with 100% absorptance at the frequency of 1.37 THz. Narrowband absorption is caused by the localized magnetic resonance. When vanadium dioxide is in the insulating state, the design behaves as a broadband absorber composed of a square-shaped graphene, topas layer, vanadium dioxide film, and metal film. It has a broadband absorption in the frequency range of 1.05-2.35 THz, and the corresponding absorptance is more than 90%. The merging of two resonances with overlapping region ensures broadband performance of the designed absorber. The working bandwidth and intensity of narrowband absorption and broadband absorption can be dynamically adjusted by changing the Fermi energy level of graphene. The influences of structure parameters are discussed on absorption performance. In addition, the designed absorber is not sensitive to incident angle. Because of the simple structure, our design can be applied to many promising fields in intelligent absorption and terahertz switch.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Multi-mode graphene based terahertz amplitude modulation enhanced by hollow cross H-structured metasurface

Physica Scripta

Liangping Xia, Yixuan Zou, Man Zhang, Wenjuan Yan, Suihu Dang, Songbai Li, Shaoyun Yin,  Hongliang Cui

https://iopscience.iop.org/article/10.1088/1402-4896/ab1bfe/pdf

A graphene-metasurface based THz amplitude modulator enhanced with the hollow cross H array in a metal film is proposed. Based on the transmission line theory, the equivalent analysis model of the modulator is built. With the model, the multi-mode resonation excited by the metasurface is analyzed and the amplitude modulations of the THz transmission are discussed. By applying modulation voltage between the metallic metasurface and graphene film in the experiment, three enhanced modes in the transmission spectrum are observed and the maximum modulation depth is enhanced to 49.3% in the band of 0.1-1.8THz. The experimental results exhibit a good agreement with the theory analysis.

Abstract-Deep Electrical Modulation of Terahertz Wave Based on Hybrid Metamaterial-Dielectric-Graphene Structure

Liangping Xia, Xin Zhang, Man Zhang, Suihu Dang, Shijian Huang, Yong Tan, Wenjuan Yan, Hong-Liang Cui

https://www.mdpi.com/2076-3417/9/3/507

A terahertz modulation structure based on hybrid metamaterial and graphene is proposed and demonstrated in this work. The metamaterial with a square slit ring array excites terahertz resonance in the slits and enhances the interaction between the terahertz wave and graphene. The graphene layer acting as the active material is tuned by the applied electrical field. With the separation by a dielectric layer between the graphene and the metallic structure, the resonant frequency and transmitted energy are both modulated by the graphene. Experimental result indicates that the modulation depth of the terahertz transmitted amplitude is 65.1% when the applied modulation voltage is tuned 5 V.