Berini P
Opt Express. 2000 Nov 6;7(10):329-35. doi: 10.1364/oe.7.000329.
The properties of some purely bound plasmon-polariton modes guided by an asymmetric waveguide structure composed of a thin lossy metal film of finite width supported by a dielectric substrate and covered by a different dielectric superstrate are presented for what is believed to be the first time. The mode spectrum supported by these structures is quite different from the spectrum supported by corresponding asymmetric slab structures or similar finite-width symmetric waveguides. Unlike these limiting cases, the dispersion with film thickness exhibits an unusual oscillatory character that is explained by a "switching" of constituent interface modes. This mode switching is unique to asymmetric finite-width structures. Above a certain cut-off film thickness, the structure can support a long-ranging mode and its attenuation decreases very rapidly with decreasing film thickness, more so than the long-ranging mode in symmetric structures. Also, the cutoff thickness of the long-ranging mode is larger than the cutoff thickness of the long-ranging mode in the corresponding asymmetric slab waveguide, which implies that propagation along finite-width films is more sensitive to the asymmetry in the structure than propagation along a similar slab structure. Both of these results are potentially useful for the transmission and control of optical radiation.
首次展示了由有限宽度的薄有损金属膜构成的非对称波导结构所引导的一些纯束缚等离子体激元-极化子模式的特性，该金属膜由电介质衬底支撑，并覆盖有不同的电介质覆盖层。这些结构所支持的模式光谱与相应的非对称平板结构或类似的有限宽度对称波导所支持的光谱有很大不同。与这些极限情况不同，膜厚度的色散呈现出一种不寻常的振荡特性，这可以通过组成界面模式的“切换”来解释。这种模式切换是不对称有限宽度结构所特有的。在一定的截止膜厚度以上，该结构可以支持一种长程模式，并且其衰减随着膜厚度的减小而非常迅速地减小，比对称结构中的长程模式更明显。此外，长程模式的截止厚度大于相应非对称平板波导中长程模式的截止厚度，这意味着沿有限宽度薄膜的传播比沿类似平板结构的传播对结构中的不对称性更敏感。这两个结果对于光辐射的传输和控制都可能是有用的。
