ABSTRACT
This chapter proposes an alternative approach to designing binary ultrathin metalenses capable of focusing linearly polarized laser light into a focal spot below the diffraction-limited size. The performance of the designed metalens was simulated using a finite-difference time-domain method in FullWAVE software. The metalens relief height is 70 nm, meaning that a 70-nm thick silicon film has been etched through as far as the substrate. The intensity in the focal spot was measured using a hollow metallized pyramid-shaped tip C having a 100-nm pinhole in the vertex. The smallest and most circular focal spot has been found to be produced by the 16-sectored metalens with space-variant gratings. When computing a metalens, an important parameter to be taken into account is the number of space-variant gratings to perform the polarization conversion. The metalenses are illuminated by plane linearly polarized TE– or TM– waves and a left-handed and right-handed circularly polarized beam. Locally, the metalenses operate as half-wave plates.
