Achieving 100% amplitude modulation depth in the terahertz range with graphene-based tuneable capacitance metamaterials.

IF 23.4 Q1 OPTICS
Ruqiao Xia,Nikita W Almond,Wadood Tadbier,Stephen J Kindness,Riccardo Degl'Innocenti,Yuezhen Lu,Abbie Lowe,Ben Ramsay,Lukas A Jakob,James Dann,Stephan Hofmann,Harvey E Beere,Sergey A Mikhailov,David A Ritchie,Wladislaw Michailow
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Abstract

Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials. Metamaterial-based active modulators can be created by placing graphene as a tuneable element shunting regions of high electric field confinement in metamaterials. However, in this common approach, the graphene is used as a variable resistor, and the modulation is achieved by resistive damping of the resonance. In combination with the finite conductivity of graphene due to its gapless nature, achieving 100% modulation depth using this approach remains challenging. Here, we embed nanoscale graphene capacitors within the gaps of the metamaterial resonators, and thus switch from a resistive damping to a capacitive tuning of the resonance. We further expand the optical modulation range by device excitation from its substrate side. As a result, we demonstrate terahertz modulators with over four orders of magnitude modulation depth (45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz), and a reconfiguration speed of 30 MHz. These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7 mS. The demonstrated approach can be applied to enhance modulation performance of any metamaterial-based modulator with a 2D electron gas. Our results open up new frontiers in the area of terahertz communications, real-time imaging, and wave-optical analogue computing.
利用石墨烯基可调谐电容超材料在太赫兹范围内实现100%的调幅深度。
要想有效控制太赫兹辐射,就需要快速高效的调制器,而且调制器的调制深度要大,这一挑战通常通过使用超材料来解决。基于超材料的有源调制器可以通过在超材料中放置石墨烯作为可调谐元件来实现高电场约束区域的分路。然而,在这种常见的方法中,石墨烯被用作可变电阻,并且通过共振的电阻阻尼来实现调制。由于石墨烯的无间隙特性,其导电性有限,因此使用这种方法实现100%的调制深度仍然具有挑战性。在这里,我们将纳米级石墨烯电容器嵌入到超材料谐振器的间隙中,从而将谐振从电阻阻尼切换到电容调谐。我们进一步扩大了光调制范围的器件激发从其衬底侧。因此,我们展示了具有超过四个数量级调制深度的太赫兹调制器(在1.68太赫兹时为45.7 dB,在2.15太赫兹时为40.1 dB),重构速度为30 MHz。这些可调谐电容调制器是电气控制的固态器件,可实现石墨烯电导率低于0.7 mS的统一调制。该方法可用于增强任何基于二维电子气体的超材料调制器的调制性能。我们的研究结果在太赫兹通信、实时成像和波光模拟计算领域开辟了新的前沿。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Light-Science & Applications
Light-Science & Applications 数理科学, 物理学I, 光学, 凝聚态物性 II :电子结构、电学、磁学和光学性质, 无机非金属材料, 无机非金属类光电信息与功能材料, 工程与材料, 信息科学, 光学和光电子学, 光学和光电子材料, 非线性光学与量子光学
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审稿时长
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