Computer simulation and experimental verification of high performance optical near-field probe by using surface plasmon polariton gap waveguide

作者提出的等离子体间隙探针具有低光噪声（孔径探针的优点）和高分辨率（散射探针的优点）的特点。在2008年和2009年，为了得到探针的最佳形状，计算了等离子体间隙波导（PGW）的复传播常数。编制并开发了基于线（MoL）法的数值计算代码。用MoL程序计算了不同形状SPGW的复传播常数。综合这些数值计算结果，发现SPGW的交错结构可以在不增加衰减常数的情况下在探针尖端产生局部化的增强光场。本文对探针尖端的光场，特别是矢量场的基本特性进行了详细的研究，发现它们强烈地依赖于探针尖端的纳米结构。这些结果进一步说明，在实际应用中，探头尖端形状的设计必须认真进行。2010年，对用于评价等离子体间隙探针的计算机仿真代码进行了改进和扩展。在从事等离子体纳米光子学研究的实验室中，大多采用基于时域有限差分方法的商用仿真代码。相反，在作者的实验室中，采用基于迭代法和快速傅里叶变换（VIE-FFT）的体积积分方程的手工模拟代码进行数值模拟。比较了时域有限差分法和VIE-FFT的仿真结果，发现VIE-FFT的仿真结果比时域有限差分法的仿真结果更准确、更有用。例如，在与英国明斯特大学的合作研究中，作者对四面体等离子体探针的光场分布进行了分析，得到了比FDTD法更精确的结果。产生这些结果的原因是由于VIE-FFT不需要时域有限差分法所必需的数值稳定性条件和吸收条件，并且难以确定最佳条件。在此基础上，针对大规模问题对VIE-FFT仿真代码进行了扩展和改进，采用openMP将软件包BLAS实现双精度并行化。少

The plasmon gap probe proposed by authors has the characteristics of low optical noise that is the advantage of the aperture probe and of high resolution that is the advantage of the scattering probe.In 2008 and 2009, the complex propagation constants of the plasmon gap waveguide (PGW) have been calculated in order to obtain the optimum shape of the probe. The code of the numerical valuation based on the method of line (MoL) has been made and developed. The complex propagation constants for various shapes of SPGW have been calculated by using the MoL code. Considering these kinds of numerical evaluations, it is found that the staggered structure of SPGW can make a localized and enhanced optical field on the probe tip without increasing the attenuation constant. The basic characteristics of the optical fields, especially vector fields, on the probe tip have been investigated in detail and it is found that they strongly depend on the nanometric structure of the probe tip. These results s … More how that the design of the shape of the probe tip must be carefully performed in the practical applications.In 2010, the computer simulation code used for the evaluation of the plasmonic gap probe, has been improved and extended. In the most of the laboratories who are investigating the subjects in the fields of the plasmonic-nanophotonics, the commercial simulation code based on the FDTD method is employed. Contrary, in the author's laboratory, the hand-made simulation code based on the volume integral equation with iteration method and fast Fourier transformation (VIE-FFT) is employed for the numerical simulations. Comparing the simulation results between by the FDTD and by the VIE-FFT, it is found that the results by VIE-FFT give the more accurate and more useful results than those by FDTD. For example, in the collaborate study with a group of Munster niversity, the authors could obtain the more accurate results than those by FDTD method for the analysis of the optical filed distribution of the tetrahedral plasmonic probe. The reason of these results is based on the facts that the VIE-FFT does not require the numerical stability conditions and absorbing conditions that are essential in the FDTD method and troublesome to set optimum conditions. Furthermore, the VIE-FFT simulation code is extended and improved for the large-scale problems by making the software packeg BLAS double precision and parallel code by the openMP. Less