双椭圆纳米金属棒构成的表面等离子体波导的传输特性分析

Propagation properties of a surface plasmonic waveguide with double elliptical metallic nanorods

设计了一种双椭圆纳米金属棒表面等离子体波导,采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率和传播长度随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个椭圆金属棒所形成的中间区域,且越靠近金属棒的弧形边,沿纵向的能流越大.通过调节两个金属棒的中心距离以及它们的两个半轴的大小,可以调节模式的有效折射率和传播长度.在工作波长确定的条件下,相对于a=b的情形来说,在a<b时,场与金属表面接触的面积较大,场与金属的相互作用较弱,有效折射率较小,传播距离较大.在几何参数确定的条件下,相对于λ=705.0nm的情形来说,在λ较大时,场的分布范围较大,场与金属表面的接触面积较大,场与金属的相互作用较弱,有效折射率较小,传播距离较长.这种双椭圆纳米金属棒表面等离子体波导可以用于光子器件集成领域和传感器领域.

We introduce a kind of surface plasmonic waveguide with double elliptical metallic nanorods. The dependence of the distribution of longitudinal energy flux density, the effective index and the propagation length of the fundamental mode with longer propagation length supported by this waveguide, on the geometrical parameters and the working wavelengths are analysed using the finite-difference frequency-domain （FDFD） method. Results show that the longitudinal energy flux density is distributed mainly in the middle area, which are formed by two elliptical metallic nanorods, and the longitudinal energy flux density is stronger closer to the arc sides of the metallic nanorods. The effective index and propagation length of the fundamental mode can be adjusted by the centric distance of two ellipses as well as the size of the two semiaxis. At a certain working wavelength, relative to the case of a = b, in the case of a 〈 b, the size of the contact area of field and metallic surface is large, the interaction of field and silver is weak, the effective index becomes small, so the propagation length becomes large. With certain geometric parameters, relative to the case of λ= 705.0 nm, in the case of larger λ, the area of field distribution is large, the size of the contact area of field and metallic surface is also large, the interaction of field and silver is weak, the effective index becomes small, so the propagation length becomes large. This kind of metallic surface plasmonic waveguide can be applied to the field of photonic device integration and sensors.