Investigation of Plasmonic Lens with Annular Structure for Laser Light Focusing

In this paper, a plasmonic lens with a continuous relief in thin metal film illuminated by a radially polarized Gaussian beam with a wavelength lambda = 633 nm was studied by the finite difference time domain method. During the study, the influence of the lens geometry and material on light focusing was analyzed. It is shown that the plasmonic lens with a central depression of 90 nm depth and 1.5 mu m in diameter and with the circular diaphragm of 5 mu m in diameter and 500 nm in width in the silver film with a thickness of 100 nm focuses laser light into a spot with FWHM = 0.37 lambda and I-max = 4.127 a.u.