Generation and characteristics of hollow structured optical fields based on multiple off-axis vortices.

In this paper, various hollow structured optical fields are generated by skillfully adjusting the number and positions of multiple off-axis vortices loaded in a Gaussian beam. The focal-field characteristics of the generated hollow structured optical fields after passing through an ordinary lens are studied based on the scalar diffraction theory. Firstly, a variety of hollow structured optical fields are theoretically simulated by adjusting the number and positions of multiple off-axis vortices loaded in the Gaussian beam. The focal-field characteristics of the hollow structured optical fields after passing through a lens are theoretically analyzed. On this basis, the experiments are implemented in the built optical system for multi-off-axis vortex beam focusing through an ordinary lens. In the experiments, various hollow structured optical fields are detected in CCD which are consistent with the theoretical results. The manipulations of size and rotation direction of the hollow structured optical fields are realized. We believe that this study will contribute to extending the potential applications of off-axis vortex beams in fields such as optical field shaping, optical manipulation and laser processing.