The feasibility of nanometric practical optical waveguide circuits based on surface plasmon polariton gap waveguides (SPGWs) is investigated in detail through three-dimensional simulations. H-plane planar branching waveguide circuits of subwavelength scale are shown to be possible using SPGWs. The waveguide characteristics of the circuits are found to be highly sensitive to the dimensions of the optical circuit, indicating that highly accurate computer-aided design and simulations are necessary for the construction of practical SPGW-based optical circuits.
A practical technique by which a strongly confined and strongly enhanced optical near-field can be created on a metallic probe-tip is investigated. The technique uses an I-shaped aperture in a pyramidal structure formed on a thick metallic screen. The pyramidal structure divided into two sections by the I-shaped aperture and one of them is used as a tapered metallic probe. A surface plasmon polariton (SPP), which is excited and enhanced in the I-shaped aperture, propagates along the side surface of the aperture and pyramidal structure and illuminate the probe-tip. Scattering of optical waves by this structure is solved numerically using a volume integral equation by a generalized minimum residual method and fast Fourier transformation. It is shown that a strongly localized and strongly enhanced optical field is created at the tip of this metallic probe by SPPs. The fundamental characteristics of the localized and enhanced optical near-field on the probe-tip are investigated.
A metallic tip probe that gives high optical intensity and small spot size with a small background light is proposed and simulated. The proposed tip probe provides advantages of both the aperture probe and the apertureless probe currently used in the scanning near-field optical microscope. The tip probe is illuminated by surface plasmon polaritons transmitted through the I-shaped aperture in a pyramidal structure on a thick metallic screen. Scattering of optical waves by this structure is solved numerically using a volume integral equation by generalized conjugate residual iteration and fast Fourier transformation. The proposed tip probe is shown to simultaneously provide both high near-field intensity and small spot size with a small background light.
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