[论文解读] Plasmonic instabilities and terahertz waves amplification in graphene metamaterials

Stéphane Boubanga Tombet, Deepika Yadav+3 more|arXiv (Cornell University)|Jan 14, 2018

Plasmonic and Surface Plasmon Research参考文献 39被引用 4

一句话总结

该论文表明，石墨烯基超材料可通过电流驱动的等离子体不稳定性实现高效的太赫兹波放大，在室温下最高可实现9%的光增益。该机制利用高迁移率石墨烯中强烈的光-等离子体耦合，抑制吸收，使外部量子效率比传统光-太赫兹转换器高出两个数量级。

ABSTRACT

Plasmon oscillations have been intensively studied for more than forty years in conventional two-dimensional electron gas systems in order to find new alternatives to the vacuum devices based on the Smith-Purcell effect in the far-infrared region. However, beside the multiple endeavors, up to date, the plasmon generation in semiconductor heterostructures has been very inefficient. Here we demonstrate that the use of high mobility graphene metamaterials, due to their well-known stronger light-plasmon coupling compared to semiconductor materials can significantly improve the efficiency of far-infrared plasmonic amplifiers and generators. We explore current-driven plasmon dynamics including perfect transparency and light amplification in monolayer graphene structures. Current-induced complete suppression of the graphene absorption is experimentally observed in a broad frequency range followed by a giant amplification (up to about 9 % gain) of an incoming terahertz radiation at room temperature. These active plasmonic processes are triggered by relatively low bias voltage in the graphene devices leading to external quantum efficiency of about two orders of magnitude higher than those of the popular optical-to-terahertz conversion devices largely used in far-infrared technologies. Our results combined with the relatively low level of losses and high degree of spatial confinement of plasmons in graphene will open pathways for a wide range of integrated high speed active optoelectronics devices.

研究动机与目标

• 解决传统半导体异质结构在远红外应用中等离子体生成效率低下的问题。
• 探索单层石墨烯中电流驱动的等离子体动力学，以实现主动太赫兹放大。
• 在石墨烯基器件中使用低偏置电压实现太赫兹辐射的显著放大。
• 展示室温运行下高外部量子效率的集成太赫兹光电集成器件。
• 利用石墨烯的强光-等离子体耦合特性与低损耗特性，实现实用化的高速有源器件。

提出的方法

• 利用高迁移率单层石墨烯超材料以增强光-等离子体耦合。
• 施加电流偏置以诱导等离子体不稳定性并抑制本征吸收。
• 在偏置条件下实验测量石墨烯结构的太赫兹透射与放大特性。
• 采用宽频率范围评估透明度与增益特性。
• 在室温条件下量化外部量子效率与增益水平。
• 分析等离子体动力学，包括完美透明与放大区域。

实验结果

研究问题

• RQ1 石墨烯超材料中的电流驱动等离子体不稳定性是否能实现高效的太赫兹波放大？
• RQ2 石墨烯在太赫兹波段在多大程度上可抑制吸收并实现净增益？
• RQ3 与传统器件相比，石墨烯基太赫兹放大器的可实现外部量子效率是多少？
• RQ4 低偏置操作如何影响石墨烯基等离子体放大器的性能？
• RQ5 石墨烯基系统能否在有源太赫兹器件中实现高空间局域化与低损耗？

主要发现

• 在宽频率范围内，实验观察到电流诱导的石墨烯吸收被抑制。
• 在室温下，对入射太赫兹辐射实现了约9%的最大放大增益。
• 该器件的外部量子效率比主流光-太赫兹转换器件高出约两个数量级。
• 放大效应由相对较低的偏置电压触发，支持实际运行。
• 该系统表现出强烈的光-等离子体耦合与低传播损耗，实现了等离子体的高空间局域化。
• 结果证明了在太赫兹波段实现集成化、高速有源光电集成器件的可行路径。