Focusing and tight-focusing properties of radially polarized Bessel-Gaussian power-exponent-phase vortex beams

In this paper, the focusing and tight-focusing properties of radially polarized (RP) Bessel-Gaussian (BG) rotationally-symmetric power-exponent-phase vortex beam (RPVBs) were investigated theoretically and experimentally. Based on the theory of vector beam, the propagation and tight-focusing models were derived to reveal the focusing and tight-focusing properties of the RP-BG-RPVBs by numerical simulation. Then, the experimental setup was established to validate that the RP-BG-RPVBs presented the fan-shaped and polycyclic intensity distribution, which possessed the features of RP beams, BG beams, and RPVBs, similarly. Thus, for normal focusing, the RP-BG-RPVBs would turn into a ring at the focal plane, of which the ring radius is almost constant and independent of the topological charge. Meanwhile, for the tight-focus, there are a secondary ring and several dark cores around the central spot due to the longitudinal component of the tightly focused RP-BG-RPVBs, of which the petal number is also equal to the topological charge. These remarkable properties of the RP-BG-RPVBs may have potential applications in optical trapping of multiple particles and laser fabrication of chiral microstructures. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement