Raad Shiva Hayati, Atlasbaf Zahra, Zapata-Rodríguez Carlos J
Department of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran.
Department of Optics and Optometry and Vision Science, University of Valencia, 46100, Burjassot, Spain.
Sci Rep. 2020 Nov 4;10(1):19060. doi: 10.1038/s41598-020-76037-x.
In this paper, the hybridized localized surface plasmon resonances (LSPRs) of a periodic assembly of graphene-wrapped nanoparticles are used to design a nanoparticle assisted optical absorber. Bandwidth enhancement of this structure via providing multiple types of plasmonic resonances in the associated unit cell using two densely packed crossly stacked graphene strips is proposed. The designed graphene strips support fundamental propagating surface plasmons on the ribbons, and gap plasmons in the cavity constructed by the adjacent sections. Graphene strips exhibit a hyperbolic dispersion region in the operating spectrum and assist in the bandwidth enhancement. Moreover, since the nanoparticles are deposited on the top strips, real-time biasing of them can be easily conducted by exciting the surface plasmons of the strip without the necessity to electrically connect the adjacent nanoparticles. The overall dynamic bandwidth of the structure, using a two-state biasing scheme, covers the frequencies of 18.16-40.47 THz with 90% efficiency. Due to the symmetry of the structure, the device performs similarly for both transverse electric (TE) and transverse magnetic (TM) waves and it has a high broadband absorption rate regarding different incident angles up to 40°. Due to the presence of 2D graphene material and also using hollow spherical particles, our proposed absorber is also lightweight and it is suitable for novel compact optoelectronic devices due to its sub-wavelength dimensions.
在本文中，石墨烯包裹的纳米粒子周期性组装体的杂化局域表面等离子体共振（LSPRs）被用于设计一种纳米粒子辅助的光吸收器。提出了通过使用两个紧密堆积的交叉堆叠石墨烯条在相关晶胞中提供多种类型的等离子体共振来增强该结构的带宽。所设计的石墨烯条在条带上支持基本的传播表面等离子体，在由相邻部分构成的腔内支持间隙等离子体。石墨烯条在工作光谱中呈现出双曲线色散区域，并有助于带宽增强。此外，由于纳米粒子沉积在顶部条带上，通过激发条带的表面等离子体可以轻松地对它们进行实时偏置，而无需将相邻的纳米粒子电连接。使用双态偏置方案时，该结构的整体动态带宽以90%的效率覆盖18.16 - 40.47太赫兹的频率。由于结构的对称性，该器件对于横向电场（TE）波和横向磁场（TM）波的表现相似，并且对于高达40°的不同入射角具有较高的宽带吸收率。由于二维石墨烯材料的存在以及使用空心球形粒子，我们提出的吸收器也是轻质的，并且由于其亚波长尺寸适用于新型紧凑型光电器件。
