A nonradiating, spatially confined optical field based on surface plasmon polaritons (SPPs) on a corrugated surface of
metal film is proposed. With the help of the surface plasmon band-gap nano-structure, SPP can be collected in a spatial
region beyond the diffraction limit and form a confined optical field, which can be used as a nano-source in near-field.
Compared with other types of near-field sources, such confined optical field provides higher intensity, and the spot size
of the nano-source can keep constant within certain distance. By using the method of Finite-Difference Time-Domain
(FDTD) is used to simulate the distributions of the confined optical field, two types of confined optical fields based on
SPPs excited by prism and by grating, respectively, are demonstrated in 2D- and 3D-space. Such confined optical field
as a nano-source, is promising to be applied to near-field imaging and optical manipulation, and has potential
applications in nano-photonics devices based on SPP.