The generation of magnetization needles and chains with fan-shaped filter

In this paper, a fan-shaped filter is optimized. Magnetization needles and magnetization chains are generated using by an angular-polarized multi-Gaussian vortex beam and the filter in single lens system and in a 4π focusing system, respectively. The depth of focus of the obtained magnetization needles is 61.2λ, which is 2.1 times that in reported magnetization needles generated by the same beam. The magnetization needles can be transformed into hollow dark channels by changing the topological charge of the incident beam. The obtained magnetization chains consist of 33 periodically arranged magnetization spots, and the depth of focus and full width at half maximum are 61.2λ and 0.36λ, respectively. Furthermore, magnetization chains can be linearly moved in the longitudinal direction by changing the phase difference of two counter-propagating vortex beams.