Diffraction of Gaussian beams by micro-cylinders with sub-wavelength radius

We analyse diffraction of Gaussian beams by silicon micro-cylinders with sub-wavelength radius by means of the finite-difference time-domain method. It is numerically shown that a Gaussian beam can be focused near the surface of the element into a light spot with the size of 0.25λ at the full width at half maximum of intensity. If silicon micro-cylinder illuminated by a laser beam with the vortex phase singularity a light spot with the longitudinal component is generated.