Modelling the Tight Focusing of Laser Beams with Radial Polarization Using Binary Mask with Optimal Configuration

The paper is dedicated to the study of tight focusing of laser beams with radial polarization and finding the optimal configuration of a binary phase mask to obtain the minimum size of the focal spot according to the full-width at half-maximum of intensity in the focus of an aplanatic lens. The simulation was implemented by the Richards-Wolf formulas for radially polarized light. Optimization of the binary phase mask was implemented by genetic algorithm. Optimal parameters were selected for binary masks consisting of 108 and 150 zones. The sizes of the obtained focal spots were equal to FWHM = 0.36 λ and FWHM = 0.32 λ, respectively.