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

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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