Terahertz beam switching by electrical control of graphene-enabled tunable metasurface

Yin Zhang,Yijun Feng,Junming Zhao,Tian Jiang,Bo Zhu

doi:10.1038/s41598-017-14493-8

Yin Zhang, Yijun Feng + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-14493-8

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Abstract

Controlling the terahertz wave, especially the dynamical and full control of terahertz wavefront, is highly demanded due to the increasing development of practical devices and application systems. Recently considerable efforts have been made to fill the ‘terahertz gap’ with the help of artificial metamaterial or metasurface incorporated with graphene material. Here, we propose a scheme to design tunable metasurface consisting of metallic patch array on a grounded polymer substrate embedded with graphene layers to electrically control the electromagnetic beam reflection at terahertz frequency. By adjusting geometric dimension of the patch elements, 360 degree reflection phase range may be achieved, thus abrupt phase shifts can be introduced along the metasurface for tailoring the reflected wavefront. Moreover, the reflective phase gradient over the metasurface can be switched between 90 and 360 degree by controlling the Fermi energy of the embedded graphene through voltage biasing, hence dynamically switching the reflective beam directions. Numerical simulations demonstrate that either single beam or dual beam dynamically switching between normal and oblique reflection angles can be well attained at working frequency. The proposed approach will bring much freedom in the design of beam manipulation devices and may be applied to terahertz radiation control.

Highlights

Manipulating electromagnetic (EM) waves in a tunable manner is highly desired in both fundamental research and practical application
We firstly design a traditional reflective metasurface that can produce abnormal reflection of terahertz beam, which consists of meta-particles of differently sized metallic patches with rectangular slot on top of a grounded polymer substrate to achieve certain phase gradient
Λ0 dΦ, 2πni dx where θi or θr is the angle of incidence or reflection respectively, λ0 is the wavelength in free space, ni is the refractive index of the incident medium, and dΦ/dx represents the phase gradient on dx range

Summary

Introduction

Manipulating electromagnetic (EM) waves in a tunable manner is highly desired in both fundamental research and practical application. The wavefront transmitted or reflected from a metasurface does rely on gradual phase changes accumulated along the optical path, and depends on abrupt phase shifts over the scale of the wavelength attained by spatially tailoring the geometry and planar arrangements of the meta-particles composing the metasurface[1] Based on this peculiar property, metasurface can mold the wavefront of the reflected and refracted beams in nearly arbitrary ways and provide complete manipulation of EM waves[6,7,8,9,10]. In this paper we present a scheme to achieve dynamical switch of THz reflection beam through tunable metasurface which employs a traditional metal/dielectric metasurface embedded with gated graphene layers. As we employ non-structured graphene layers as controlling element, the proposed metasurfaces may provide feasible examples of bridging the theory and possible experimental realizations in tunable graphene devices

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