Kim Shinho, Menabde Sergey G, Cox Joel D, Low Tony, Jang Min Seok
Opt Express. 2021 Apr 26;29(9):13852-13863. doi: 10.1364/OE.423691.
The extreme field confinement and electro-optic tunability of plasmons in graphene make it an ideal platform for compact waveguide modulators, with device footprints aggressively scaling orders of magnitude below the diffraction limit. The miniaturization of modulators based on graphene plasmon resonances is however inherently constrained by the plasmon wavelength, while their performance is bounded by material loss in graphene. In this report, we propose to overcome these limitations using a graphene-covered λ/1000 plasmonic nanogap waveguide that concentrates light on length scales more than an order of magnitude smaller than the graphene plasmon wavelength. The modulation mechanism relies on interference between the non-resonant background transmission and the transmission mediated by the gate-tunable nanogap mode, enabling modulation depths over 20 dB. Since the operation of the device does not rely on graphene plasmons, the switching behavior is robust against low graphene carrier mobility even under 1000 cm/Vs, which is desirable for practical applications.
石墨烯中等离子体激元的极端场限制和电光可调性使其成为紧凑型波导调制器的理想平台，其器件尺寸大幅缩小至衍射极限以下几个数量级。然而，基于石墨烯等离子体激元共振的调制器的小型化本质上受到等离子体激元波长的限制，而其性能则受石墨烯中的材料损耗限制。在本报告中，我们提出使用覆盖有石墨烯的λ/1000等离子体纳米间隙波导来克服这些限制，该波导能将光集中在比石墨烯等离子体激元波长小一个数量级以上的长度尺度上。调制机制依赖于非共振背景传输与由栅极可调纳米间隙模式介导的传输之间的干涉，可实现超过20 dB的调制深度。由于该器件的运行不依赖于石墨烯等离子体激元，即使在低于1000 cm²/V·s的低石墨烯载流子迁移率下，其开关行为也很稳健，这对于实际应用来说是很理想的。
