Circularly-symmetric alternating optical vortex lattices and their focusing characteristics

We report an experimental realization of circularly- symmetric optical vortex lattices (OVLs) with alternating positive and negative topological charges of order ±n, termed the nth-order circularly-symmetric alternating OVL (CSAOVL). The focusing fields of these CSAOVLs exhibit the intriguing periodic patterns with a period of 4 for different n values, and their intensity and phase distributions can be regulated via radial and azimuthal parameters. Particularly, when n is a multiple of 4, the resulting central bright spot in the focusing fields is significantly smaller than a Gaussian spot. These findings advance the exploration of structured OVLs and open up potential applications in particle manipulation, imaging, and complex optical potentials.