Focusing Properties of Annular Cylindrical Vector Beam Induce by Tunable Mask

Focusing properties of annular cylindrical vector beam induced by tunable mask is numerically investigated in this paper. The tunable mask which may alter the wavefront of incident beam with tunable polarization, phase, and the geometrical parameter radius of the field. Numerical simulations show that the evolution of the focal shape is altered considerable by changing the radius of the tunable annular mask. Increase inner radius of the annular zone, focal spots shift and broaden along optical axis. In this process, the focal depth increases. By spatially varying phase and rotating the direction of polarization of the field, we adapt the field distribution in the focal region. Polarization adds a new degree of freedom and leads to some novel results as shown in this paper, which predicts that this is an interesting method in using pupils functions which are easier to be produced to obtain focal shift and high focal depth. The tunable focal shift is also discussed to construct controllable optical tweezers.