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

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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