Concentric piecewise vector beam for superresolution and high focal depth

Abstract

Resolution and focal depth are very important parameters in optical data storage systems, and have attracted much attention. In this article, focusing properties of concentric two-zone cylindrical vector beam are investigated theoretically by means of vector diffraction theory. The phase shift of the center zone and outer annular zone are different. Simulation results show that the focal pattern can be altered considerably by adjusting the radius of dividing circle between the two concentric portions and the phase shift of each zone. For certain phase shifts for these two zone, focal spot broadens along optical axis with increasing radius, and splits into two peaks, and then combine back into one peak again. In this evolution process, some novel focal pattern may come into being. For certain geometrical parameter and phase shift, the focal spot shrinks, which means superresolution effect appears, and at the same time, focal depth can also be widened, high focal depth companies with resolution, which is very useful in optical data storage systems.