近日，英国剑桥大学Michailow, Wladislaw团队报道了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。2025年8月4日出版的《光：科学与应用》杂志发表了这项最新研究成果。

要想有效控制太赫兹辐射，就需要快速且高效的调制器，且调制器的调制深度要大，而这一挑战通常由主题化的超材料来解决。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，石墨烯是一个可变电阻，调制是通过共振的电阻阻尼来实现的。由于石墨烯的无间隙特性，其导电性有限，因此实现100%调制深度仍然具有挑战性。

研究组将纳米级石墨烯电容器嵌入超材料谐振器的间隙中，从而从电阻阻尼切换到谐振的电容调谐。他们通过从基板侧的器件激发进一步扩展了光学调制范围，展示了具有超过四个数量级调制深度（1.68THz为45.7dB，2.15THz为40.1dB）和30MHz重构速度的太赫兹调制器。

这些可调电容调制器是电控固态器件，能够实现石墨烯电导率低于0.7mS的单位调制。所演示的方法可以应用于增强任何基于超材料的调制器在二维电子气中的调制性能。该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领域。

附：英文原文

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

Author: Xia, Ruqiao, Almond, Nikita W., Tadbier, Wadood, Kindness, Stephen J., DeglInnocenti, Riccardo, Lu, Yuezhen, Lowe, Abbie, Ramsay, Ben, Jakob, Lukas A., Dann, James, Hofmann, Stephan, Beere, Harvey E., Mikhailov, Sergey A., Ritchie, David A., Michailow, Wladislaw

Issue&Volume: 2025-08-04

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 (45.7dB at 1.68THz and 40.1dB at 2.15THz), and a reconfiguration speed of 30MHz. These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7mS. 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.

DOI: 10.1038/s41377-025-01945-4

Source: https://www.nature.com/articles/s41377-025-01945-4