Open AccessGeneration of equilateral-polygon-like flat-top focus by tightly focusing radially polarized beams superposed with off-axis vortex arrays
Author(s) -
Xiaolei Wang,
Bowen Zhu,
Dong Yu,
Shuai Wang,
Zhuqing Zhu,
Bo Fang,
Xiangping Li
Publication year - 2017
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.25.026844
Subject(s) - optics , physics , vortex , diffraction , optical axis , equilateral triangle , optical vortex , focus (optics) , numerical aperture , lens (geology) , geometry , beam (structure) , wavelength , mathematics , thermodynamics
In this paper, the general formula for tightly focusing radially polarized beams (RPB) superposed with off-axis vortex arrays is derived based on Richard-Wolf vector diffraction theory. The off-axis vortex breaks the rotational symmetry of the energy flow along the axial direction and leads to the spatial redistribution of intensity within the focal plane. The dependence of the consequent focal intensity redistribution on the off-axis distance of vortices as well as the numerical aperture of the lens is theoretically studied. Based on this intriguing feature, generation of equilateral-polygon-like flat-top focus (EPFF) with a flat-top area on the level of sub-λ 2 is realized. The demonstrated method provides new opportunities for focus shaping and holds great potentials in optical manipulation and laser fabrication.