Converting transverse photons into longitudinal two-dimensional plasmon-–polaritons (2D-PP) and vice versa presents a significant challenge within the fields of photonics and plasmonics. Therefore, understanding the mechanism which increases the photon – 2D-PP conversion efficiency could significantly contribute to those efforts. In this study, we theoretically examine how efficiently incident radiation, when scattered by a silver spherical nanoparticle (Ag-NP), can be transformed into 2D-PP within van der Waals (vdW) heterostructures composed of hexagonal boron nitride and graphene (hBN/Gr composites). We show that the Dirac plasmon (DP) excitation efficiency depends on the Ag-NP radius as R 3, and decreases exponentially with Ag-NP height h, so that for a certain Ag-NP geometry up to 25 % of the incident electrical field is channeled into the DP. We demonstrate that the linear plasmons (LPs) excitation efficiency can be manipulated by changing the graphene–graphene distance Δ (or hBN thickness) or by changing the number of graphene layers N. By increasing Δ and/or N the LPs move towards smaller wave vectors Q and become accessible by the Ag-NP dipole field, so that for N ≥ 5 the excitation of more than one LP is possible. These results are supported by recent scattering-type scanning near-field optical microscopy (s-SNOM) measurements. Furthermore, we show that Ag-NPs with specific parameters preferentially hybridizes with DPs of a particular wavelength λ D , facilitating selective excitation of DPs. The obtained tuning possibilities could have a significant impact on applied plasmonics, photonics or optoelectronics.

中文翻译：

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石墨烯/六方氮化硼范德华异质结构中的光驱动等离子激元：模拟 s-SNOM 测量

将横向光子转换为纵向二维等离子体激元（2D-PP），反之亦然，这在光子学和等离子体激元领域提出了重大挑战。因此，了解提高光子 - 2D-PP 转换效率的机制可以为这些努力做出重大贡献。在这项研究中，我们从理论上研究了当入射辐射被银球形纳米粒子（Ag-NP）散射时，如何有效地将其转化为由六方氮化硼和石墨烯（hBN/）组成的范德华（vdW）异质结构内的2D-PP Gr 复合材料）。我们证明狄拉克等离子体 (DP) 激发效率取决于 Ag-NP 半径，如下所示右 3，并随着 Ag-NP 高度呈指数下降H，因此对于特定的 Ag-NP 几何形状，高达 25% 的入射电场被引导到 DP 中。我们证明，可以通过改变石墨烯-石墨烯距离 Δ（或六方氮化硼厚度）或改变石墨烯层数来控制线性等离子体（LP）激发效率氮。通过增加 Δ 和/或氮LP 向更小的波矢量移动问并可被 Ag-NP 偶极子场访问，因此对于氮≥ 5 可以激励多个 LP。这些结果得到了最近的散射型扫描近场光学显微镜（s-SNOM）测量的支持。此外，我们表明具有特定参数的 Ag-NP 优先与特定波长的 DP 杂交λ D ，促进DP的选择性激发。所获得的调谐可能性可能会对应用等离子体学、光子学或光电子学产生重大影响。