The investigation of Laguerre-Gaussian (0,1) mode focusing in the near-field diffraction by subwavelength variable-height ring gratings

The parameters of the height of individual zones of subwave ring gratings were established in this paper for which the formation of a long light needle (7.85 wavelengths) is observed in the near diffraction zone with azimuthal polarization of laser radiation. The possibility of reducing the focal spot size to 0.31 wavelengths with circular polarization of the Laguerre-Gauss mode (0,1) was also shown.