Enhancement of focusing properties of Bessel-like beam by metallic surface nanostructure

The focusing properties of a Bessel-like beam emitted from a circular slit surrounded by a surface groove (CSSG) were explored using experimental and numerical methods. The optical properties of the light emitted from the CSSG can be enhanced by using the scattered light from the surface groove. Furthermore, different modes of cylindrical surface plasmons in the circular slit are induced by different wavelengths of incident light, and beam shapes with a single spot and doughnut are created under illumination in the ultraviolet and visible regimes, respectively. A versatile beam shape is obtained from the CSSG structure.