Generation of an ultralong pure longitudinal magnetization needle with high axial homogeneity using an azimuthally polarized beam modulated by pure multi-zone plate phase filter

Based on the vector diffraction theory and the inverse Faraday effect in the magneto-optic film, light-induced magnetization distributions, for a high numerical aperture focusing configuration with an azimuthally polarized beam modulated by an optimized pure multi-zone plate phase filter, are investigated. By making use of the compeletely destructive interference of its inter circle with the π phase shift between adjacent sub-annuli, and the capability to extend the constructive interference in the propagating direction through its narrow outer annulus modulated by three misplaced helical phases, an ultralong ($107\lambda$) magnetization needle with both transverse super-resolution ($0.37\lambda$) and uniform axial field strength is achieved in the focal region. The perfect magnetization needle and the accessible method give a guide for ultrahigh density magnetic storage, fabricating magnetic lattices for spin wave operation, as well as atomic trapping. (paper)