Abrupt autofocusing performance of a circular Airyprime beam with vortex pairs

Abrupt autofocusing performance of a circular Airyprime beam (CAPB) with vortex pairs propagating in free space is investigated. Here the vortex pairs are off-axis by default. The influences of topological charges and spatial location of vortex pairs on abrupt autofocusing behaviour of a CAPB with vortex pairs are evaluated by numerical simulations. A intensity contrast, which is the ratio of peak intensity on a certain observation plane to that on initial plane, is used to describe the abrupt autofocusing ability. The focus length of a CAPB with vortex pairs only depends on topological charges and is independent of spatial location of vortex pairs. When the topological charges increase, the abrupt autofocusing ability is enhanced, which is accompanied by the slight extension of the focal length. The spatial location of vortex pairs includes azimuth and radial locations. The effect of the azimuth location of vortex pairs on the abrupt autofocusing behaviour is so slight that it can be neglected. If the radial location of vortex pairs decreases, the abrupt autofocusing ability is improved. Abrupt autofocusing performance of a CAPB with vortex pairs is also compared with that of a CAPB with an optical vortex. Due to large dark-hollow intensity distribution and carrier of much orbital angular momentum, a CAPB with vortex pairs has advantages over a CAPB with an off-axis optical vortex in optical capture and other applications.