Internal excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip
Internal excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip
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DOI：
10.1103/physreva.75.063822
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发表时间：
2007-06-01
影响因子：
2.9
通讯作者：
Maier, S. A.
中科院分区：
文献类型：
--
作者：
Ding, W.;Andrews, S. R.;Maier, S. A.
我们从理论上研究了锥形光纤的径向极化波导模式转换成表面等离子体极化子（SPPs）在无孔镀银光学尖端外表面的传播。该过程的优化对于在扫描近场光学显微镜中利用SPP超聚焦而不需要外界照明具有重要意义。我们的方法是基于分析局部模态指数随光纤半径的变化。分析了模态投影、模态耦合和金属耗散的影响，采用数值有限积分技术对辐射耦合进行了模拟。结果确定和量化需要考虑的模式转换过程。我们估计，在未涂覆的光纤锥中，至少有10%的模态能量可以输入到镀银尖端的超聚焦模式中。
We have theoretically studied the conversion of radially polarized waveguide modes of a tapered optical fiber into surface plasmon polaritons (SPPs) propagating at the outer surface of an apertureless silver-coated optical tip. Optimization of this process is important in exploiting SPP superfocusing in scanning near-field optical microscopy without the need for external illumination. Our approach is based on analyzing the evolution of the local modal index as a function of the fiber radius. The influence of mode projection, intermodal coupling, and metal dissipation are treated analytically, while a numerical finite integration technique is used to model radiation coupling. The results identify and quantify the mode conversion processes that need to be taken into account. We estimate that at least 10% of the modal energy in an uncoated fiber taper can be fed into the superfocusing mode at a silver-coated tip.