Polarization Switches Phenomena of Tight Focusing of an Azimuthally Polarized Beam Through a High Numerical Aperture Lens

By using the Richards-Wolf vector diffraction theory,the polarization properties in focused area of a double-ring-shaped azimuthally polarized beam through an annular high numerical aperture lens are studied in this paper.Numerical calculations are performed to compare the influence of corresponding parameters on the tight polarization properties.It is shown that tight focusing of a double-ring-shaped azimuthally polarized beam can change the polarization direction of the inner ring in the focal field.The correlated parameters changed,the polarization direction shows gradual change and controllable polarization switch occurred.