Free-space propagation of double-ring perfect optical vortex beams

Single-ring perfect optical vortex (SR-POV) beams have received significant attention from the singular optics community due to their topological charge (TC)-independent ring radius, which offers certain advantages over conventional vortex beams such as Laguerre-Gaussian (LG) and Bessel-Gaussian (BG) beams in applications like particle trapping, optical communication, and imaging. However, the generation of double-ring perfect optical vortices (DR-POVs), embedded with two TCs, offers greater advantages over SR-POVs in terms of robustness during propagation and enhanced channel capacity in communication networks. In our theoretical analysis, we first highlight the differences between true and approximated representations of DR-POV beams. We then investigate the propagation of DR-POV beams in free-space, demonstrating how their evolution is influenced by factors such as the TCs of the inner and outer rings and the ratio of the beam radius to beam width at the waist plane. Similar to SR-POV beams, DR-POV beams exhibit non-diffracting behavior over short propagation distances, with little to no impact on the beam's propagation when the TCs of the inner and outer rings are altered. However, phase wandering characteristics are observed, even over short propagation distances. Our research could find potential applications in the field of free-space optical communication.