Plasmonic and photonic isolators based on the spatiotemporal modulation of graphene
Plasmonic and photonic isolators based on the spatiotemporal modulation of graphene
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DOI：
10.1117/12.2519237
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
D. Correas-Serrano;N. K. Paul;J. S. Gómez-Díaz
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文献类型：
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作者：
D. Correas-Serrano;N. K. Paul;J. S. Gómez-Díaz
我们探索了石墨烯电导率的时空调制在太赫兹和红外频率下实现无磁隔离器的可能性。为此，石墨烯被加载了时间调制的周期性分布门。首先，我们研究了基于各种机制的等离子体隔离器，如不对称带隙和带间光子跃迁，我们展示了使用实际偏压方案的隔离级别超过30 dB。为了减少对高质量石墨烯的依赖，我们引入了一种混合光子平台，该平台基于时空调制的石墨烯与介电波导上传播的高q模式耦合。我们利用由于波导宽度有限而出现的横向法布里-珀罗共振，显著增强了石墨烯/波导的相互作用，并在低偏置电压调制的紧凑结构中实现了50 dB以上的隔离电平。该平台与cmos兼容，总体损耗低于4 dB，并且对石墨烯缺陷具有很强的抗冲击性。我们还提出了一个基于耦合模式理论和求解调制结构特征态的理论框架，该框架与全波数值模拟非常吻合，揭示了控制所提出的隔离器的基本物理，并加快了隔离器的分析和设计。我们设想所提出的技术将为实现集成和硅兼容的隔离器开辟新的有效途径，在通信和光子网络中具有广泛的应用。
We explore the possibilities enabled by the spatiotemporal modulation of graphene’s conductivity to realize magnetic-free isolators at terahertz and infrared frequencies. To this purpose, graphene is loaded with periodically distributed gates that are time-modulated. First, we investigate plasmonic isolators based on various mechanisms such as asymmetric bandgaps and interband photonic transitions and we demonstrate isolation levels over 30 dB using realistic biasing schemes. To lessen the dependence on high-quality graphene able to support surface plasmons with low damping, we then introduce a hybrid photonic platform based on spatiotemporally modulated graphene coupled to high-Q modes propagating on dielectric waveguides. We exploit transversal Fabry-Perot resonances appearing due to the finite-width of the waveguide to significantly boost graphene/waveguide interactions and to achieve isolation levels over 50 dB in compact structures modulated with low biasing voltages. The resulting platform is CMOS-compatible, exhibits an overall loss below 4 dB, and is robust against graphene imperfections. We also put forward a theoretical framework based on coupled-mode theory and on solving the eigenstates of the modulated structure that is in excellent agreement with full-wave numerical simulations, sheds light in the underlying physics that govern the proposed isolators, and speeds-up their analysis and design. We envision that the proposed technology will open new and efficient routes to realize integrated and siliconcompatible isolators, with wide range of applications in communications and photonic networks.