Methods for generating a dark spot using phase and polarization modulation light

A dark spot surrounded by light completely, no matter in two-dimensional or three-dimensional, has attracted more and more attention recently, owing to its recommendable applications such as the erase hollow spot for STED fluorescence microscope, the optical trap for cold atoms and the optical tweezers for precise manipulation. The main method to generate a dark spot is beam shaping, by modulating the phase and polarization of the given polarized beam with a proper phase plate. In this paper, most common realization methods for achieving various dark spots with circular polarization beam were summarized and simulated. And several special foci generated with cylindrical polarization beams were first designed, simulated and proposed. The feature and characteristic of dark spots are presented by intensity contour maps. Applications of each dark spot are also discussed according to its characteristic.