Surface plasmon gap waveguide wcich creates stiongly enhanced and confined optical near-field

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In the design of optical circuits by using SPGW, one of the most fundamental and important parameters is the propagation constant of guided waves. Since the metals are dielectric objects with complex permittivity in the optical frequency region, the propagation constant of guided waves in the SPGW has complex value inevitably, i.e., attenuation constant and phase constant. The excitation of guided waves by the practical techniques and propagation characteristics of excited guided-waves in SPGW will be important for experimental study of SPGW. Numerical techniques of computation of propagation constants by integral equation method will be also important, because integral equation method are often used in the simulation in nanophotonics.The guided waves in the surface plasmon polariton gap waveguide (SPGW) excited by the Gaussian beam through the I-shaped aperture have been investigated by the three-dimensional simulations using a volume integral equation. Optical fields excited in the S … More PGW are investigated under practical conditions. The complex propagation constants are calculated from the simulated optical fields using the least-squares fitting. The dependence of the propagation constant, i.e., attenuation and phase constants, on the gap-width and on the gap-depth of SPGW is investigated. Using above-mentioned results, the three-dimensional (3D) imaging simulations using the SPGW are performed as an example of the high performance of the SPGW under practical conditions. Simulations of imaging for a nanometric dielectric object demonstrate that the probe functions as expected in illumination mode, collection-reflection mode, and collection mode with resolution approximately correspondent to the tip diameter of the probe.A number of 3D imaging simulations for NSOM using aperture and scattering probes under practical conditions have been reported. However, most simulations examining the relationship between resolution and tip radius in NSOM using a scattering probe have been performed on the assumption that the probe tip is approximated by a small and isolated spherical object with radius equal to the tip radius. However, under practical conditions, incident light is scattered not just by the tip, and the additional scatter degrades the resolution. Imaging simulations of NSOM under practical condition without the assumption of a simple spherical probe tip thus remain important. The simulations were conducted without such an assumption in order to determine the characteristics and performance of the PGP under practical conditions in this research. Less