Numerical analysis for lacarized and ehnhaneed surface plasmon polariton of near field of dumbbell-Shaped aperture in the metallic screen.

金属屏亚波长孔径附近的近场光学特性是近场光学技术研究的重要内容。孔径扫描近场光学显微镜（孔径SNOM）是这项技术最显着的应用，并提供分辨率约等于亚波长孔径的尺寸。在这些应用中的孔径小于在探头中传播的模式的截止半径，结果是所有模式都进入截止，并且孔径仅发射输入功率的极小部分。孔径不能任意减小，因为必须确保最低水平的发射。因此，低透射率（在孔径处观察到的低光强）成为限制孔径SNOM分辨率的主要因素。因此，光学探针的优化设计对近场光学显微镜技术的发展具有重要意义。 关于我们 到目前为止，亚波长孔径被认为是与较小光斑尺寸的折衷。然而，本作者最近提出了一种I形在金属屏幕中的（哑铃形）孔径同时提供高发射强度和小光斑尺寸，并且已经表明这种有趣的特性是由于孔径内激发的表面等离子体激元（SPP）。在该项目中，详细研究了厚金属屏中I形孔近场强度与各种参数的关系，并且优化了I形孔径的设计，以获得高的近场强度和小的光斑尺寸。数值求解了光波在I形光阑上的散射，计算了光阑的近场强度和散射截面。采用广义共轭残数（CGR）迭代和快速傅里叶变换（FTT），利用体积积分方程（VIE）数值求解。少

The characteristics of optical near-fields around subwavelength apertures in metallic screens are important in research on near-field optical (NFO) technology. The aperture-scanning near-field optical microscope (aperture SNOM) is the most notable application of this technology, and offers resolution approximately equivalent to the dimensions of the subwavelength aperture. The aperture in these applications is smaller than the cutoff radius of the modes propagating in the probe, with the result that all modes run into cutoff and the aperture emits only an extremely small fraction of the input power. The aperture diameter cannot be reduced arbitrarily because a minimum level of emission must be ensured. Low transmission, observed as low light intensity at the aperture, therefore becomes the primary factor limiting the resolution of aperture SNOM. Optimization of the optical probe is therefore of great importance for advancement of the SNOM technique.Increasing the near-field intensity o … More f a subwavelength aperture has thus far been considered to be a trade off with smaller spot size. However, the present authors have recently proposed an I-shaped (dumbbell-shaped) aperture in a metallic screen that provides both high emission intensity and small spot size simultaneously, and have shown that this interesting characteristic is due to the surface plasmon polariton (SPP) excited inside the aperture.In this project, the dependence of the near-field intensities of the I-shaped aperture in a thick metallic screen on various parameters are investigated in detail, and the design of the I-shaped aperture is optimized so as to obtain high near-field intensity and small spot size. The scattering of optical waves scattered by the I-shaped aperture is solved numerically and the near-field intensities and scattering cross-sections of the aperture are calculated. The solutions are obtained numerically using a volume integral equation (VIE) by generalized conjugate residual (CGR) iteration and fast Fourier transformation (FTT). Less