十字结构银纳米线的表面等离极化激元分束特性

金属纳米线波导可以将光局域在亚波长尺度内传播, 在纳米光子集成回路方面有着重要的作用. 本文应用有限元方法, 研究了十字结构银纳米线的表面等离极化激元分束特性. 结果表明, 不同模式的表面等离极化激元在十字结构三个分支的输出依赖于端面的几何结构参数. 此外, 研究还发现由于不同模式表面等离极化激元叠加, 在十字结构的分支上出现了周期性电场分布.

Surface plasmon polaritons splitting properties of silver cross nanowires

Since metallic nanowires can confine light in nanoscale beyond the diffraction limit, metallic nanowires play an important role in nanophotonic integrated circuits. In this paper, a silver nanowire waveguide with a cross is proposed and its surface plasmon polaritons (SPPs) splitting properties of the cross at λ = 532 nm are studied by the finite element method. The nanowire has a square shape with its side length of a. Results show that the outputs for different input modes depend on the geometric parameters of the nanowires. For SPPs with TM₀ mode, there are similar intensities in different waveguide directions with smaller side length. With the increase of a, the intensity in the original waveguide direction increases monotonically, and those in the perpendicular direction will decrease monotonically. For SPPs with HE₁ mode and HE_-1 mode, most of the energy propagate along the original waveguide direction for smaller a. With the increase of a, the intensity in the original waveguide direction decreases dramatically. For SPPs with HE₁ mode, the cross blocks most of the energy in three directions for larger a. In addition to the splitting effect of it, the cross also performs a function of mode conversion. For the input SPPs with TM₀ mode, the output of SPPs along the perpendicular waveguide direction can be converted to the HE_-1 mode. For the input SPPs with HE₁ mode, the output of SPPs along the perpendicular waveguide direction can be converted to the TM₀ mode. Due to the superposition of electric fields of different SPPs modes in the perpendicular waveguide direction occur the steady-state and periodic electric field distributions.