Graphene-assisted high-efficiency liquid crystal tunable terahertz metamaterial absorber.

Lei Wang,Wei Hu,Yanqing Lu,Shijun Ge,Makoto Nakajima

doi:10.1364/oe.25.023873

Abstract

In this paper, few-layer porous graphene is integrated onto the surface of a metasurface layer to provide a uniform static electric field to efficiently control liquid crystal, thereby enabling flexible metamaterial designs. We demonstrate a tunable cross-shaped metamaterial absorber with different arm lengths driven by this combined metasurface and graphene electrode. The resulting absorber supports a resonant frequency tunable from 0.75 to 1 THz with a high-quality factor, and amplitude modulation of ~80% at these frequencies with an applied voltage of 10 V. Furthermore, the near-field intensity and hot spot distribution can be manipulated over a broad range.

Highlights

With recent rapid developments in terahertz (THz) technology, THz radiation has been used in applications as diverse as security screening, biological medical, and high-speed wireless communication [1,2,3]
Few-layer porous graphene is integrated onto the surface of a metasurface layer to provide a uniform static electric field to efficiently control liquid crystal, thereby enabling flexible metamaterial designs
We demonstrate a tunable cross-shaped metamaterial absorber with different arm lengths driven by this combined metasurface and graphene electrode

Summary

Introduction

With recent rapid developments in terahertz (THz) technology, THz radiation has been used in applications as diverse as security screening, biological medical, and high-speed wireless communication [1,2,3]. The options are limited for designing high-performance TMAs. In addition, metasurfaces used as electrodes only supply a nonuniform static electric field, especially in thin LC layers, and this does not allow efficient control of the LCs due to the fringe field effect [11], unless a very high voltage is applied. If high-performance metamaterials can be used to supply a uniform static electric field to an LC, it may be possible to further improve the efficiency and tunable range. The graphene film still has seven times the resistance of ITO and can only supply a uniform static electric field to control the LC without THz enhancement. We demonstrate an LC widely tunable THz metamaterial absorber in the far-field and in the near-field based on the integrated electrode with low operating voltage.

Schematic and principle

Simulations

Experiments

Conclusions