Generation of super-resolution longitudinally polarized beam with ultra-long depth of focus using radially polarized hollow Gaussian beam

Based on vector diffraction theory, we research how a radially polarized hollow Gaussian beam can be tightly focused by a high numerical aperture lens. A sub-wavelength longitudinally polarized beam of high beam quality and flat-topped focal shape can be obtained by properly selecting the truncation parameter and the beam order. By further introducing phase or amplitude filters, respectively, the super-resolution longitudinally polarized beam with an ultra-long depth of focus and high conversion efficiency is realized. These focusing features can be used in beam lithography, particles trapping and high-resolution imaging.