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

金属屏亚波长光圈附近的光学近场特性是近场光学(NFO)技术研究的重要内容。孔径扫描近场光学显微镜(孔径SNOM)是这项技术最引人注目的应用，它提供了大约相当于亚波长孔径的分辨率。在这些应用中，孔径小于在探测器中传播的模的截止半径，结果是所有模都进入截止，并且孔径只发射输入功率的极小部分。孔径不能任意减小，因为必须确保发射的最小水平。因此，低透过率是限制孔径SNOM分辨率的主要因素，也就是在孔径上观察到的低光强。因此，光学探头的优化对于提高近场光学显微镜技术具有重要意义。提高…的近场强度到目前为止，更多的亚波长孔径被认为是与较小的光斑尺寸进行权衡。然而，最近作者提出了在金属屏上同时提供高发射强度和小光斑尺寸的I型(哑铃形)孔，并证明了这一有趣的特性是由于孔内激发的表面等离子激元(SPP)。在本项目中，详细研究了厚金属屏中I型孔的近场强度与各种参数的关系，并对I型孔的设计进行了优化，以获得高的近场强度和小的光斑尺寸。数值求解了光波在工字形孔板上的散射，计算了孔板的近场强度和散射截面。通过广义共轭残量(CGR)迭代和快速傅立叶变换(FTT)，利用体积积分方程(VIE)数值求解。较少

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