Institute of Electromagnetics and Acoustics, and Department of Electronic Science, Xiamen University, Xiamen 361005, China.
Nanoscale. 2019 Feb 14;11(7):3229-3239. doi: 10.1039/c8nr09157a.
In this paper, we numerically demonstrate a variety of broadband optical waveguide modulators based on the hybrid surface plasmon polariton (HSPP) concept for near-infrared applications. The modulator is composed of strongly coupled double-layer graphene and double rectangle cross-sectional metal nanoribbons separated by three Al2O3 spacers, which are interpolated in a SiO2 waveguide. Owing to the unique strong coupling of HSPPs between metal nanoribbons, the subwavelength confinement, the in-plane electric field component, the light-graphene interaction, and the modulation effect of the modulator are significantly enhanced. The results show the proposed modulator achieves an outstanding performance with a modulation depth (MD) over 2.3 dB μm-1 and a small normalized mode area of ∼10-5 in a wide range of wavelength from 1.3 to 1.8 μm. By optimizing the separation of the double rectangle metal nanoribbons at the telecommunication wavelength of 1.55 μm, the modulator exhibits a high MD of 3.12 dB μm-1, a small footprint of 1.8 μm2, an ultra-wide 3 dB modulation bandwidth of 380.23 GHz, and an ultra-low energy consumption of 29.39 fJ per bit. Furthermore, we also demonstrate a modulator based on two properly apart semicircular (rhombus) metal nanoribbons with a drastically enhanced MD of 11.3 (6.32) dB μm-1 at 1.55 μm. Benefitting from the strong subwavelength confinement and excellent broadband modulation performance, the proposed optical waveguide modulators offer a significant potential to realize various long-wave near-infrared integrated modulators, interconnects and optoelectronic devices.
本文数值演示了多种基于混合表面等离子体激元（HSPP）概念的近红外宽带光波导调制器。该调制器由双层强耦合石墨烯和双矩形横截面金属纳米带组成，中间由三个 Al2O3 间隔层隔开，嵌入在 SiO2 波导中。由于金属纳米带之间的 HSPP 的独特强耦合，亚波长限制、平面内电场分量、光与石墨烯的相互作用以及调制器的调制效果都得到了显著增强。结果表明，所提出的调制器在 1.3 到 1.8 μm 的宽波长范围内实现了超过 2.3 dB μm-1 的调制深度（MD）和小于 10-5 的归一化模式面积的出色性能。通过优化双矩形金属纳米带在电信波长 1.55 μm 处的间隔，调制器表现出 3.12 dB μm-1 的高 MD、1.8 μm2 的小占空比、380.23 GHz 的超宽 3 dB 调制带宽和 29.39 fJ 每比特的超低能耗。此外，我们还展示了一种基于两个适当隔开的半圆形（菱形）金属纳米带的调制器，在 1.55 μm 处的 MD 大幅增强至 11.3（6.32）dB μm-1。得益于强亚波长限制和优异的宽带调制性能，所提出的光波导调制器为实现各种长波近红外集成调制器、互连和光电设备提供了重要的潜在应用。
