Sharp Focusing of Light by Metasurface
The refraction of light from the diffractive optical element (DOE) was simulated using the finite-difference time-domain method, then using Rayleigh–Sommerfeld integral we calculate a light field distribution at a distance of z = 200 nm from the DOE. The radially polarized light is known to be focused into a circular spot, as distinct from the linearly polarized light generating an elliptic focal spot. The polarizers P1 and P2 served the double purpose of verifying that the light incident on the micropolarizer was linearly polarized and attenuating the light power. The incident light is a mixture of linearly and radially polarized beams generated by reflecting a linearly polarized Gaussian beam at a gold 100 µm × 100 µm four-sector subwavelength diffractive optical microelement, with the sector gratings of period 400 nm and microrelief depth 110 nm. The linear polarization of the light outgoing from the splitting cube and incident on the micropolarizer was checked using a standard polarizer.