Improving near-field confinement of a bowtie aperture using surface plasmon polaritons

Bowtie aperture is known to produce subdiffraction-limited optical spot with high intensity. In this work, we investigate integrating a bowtie aperture with circular grooves to reduce the divergence of the near-field produced by the bowtie aperture. Numerical results indicate that surface waves reflected from circular grooves improve the field confinement of a bowtie aperture along the polarization axis. These circular grooves with period near half the wavelength of surface plasmon polaritons reduce the spot size by as much as 40% at distances between 20 and 100 nm from the surface and create a more symmetrical optical spot.

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