Focusing properties of Gaussian beam with superimposed left-handed and right-handed helical phase fronts

Vector diffraction theory is employed to investigate the focusing properties of the Gaussian beams with superimposed left-handed and right-handed helical phase fronts theoretically. Numerical simulations show that the intensity distribution in focal region can be altered considerably by adjusting topological charge m corresponding to right-handed helix and topological charge n corresponding to left-handed helix. Many novel focal pattern may occur. It was shown that the focal pattern evolves from one intensity peak to multiple intensity peaks with changing the topological charge m and n, and all the intensity peaks form in a circle. As the number of intensity peaks is the sum of m and n, the focal pattern can be controlled through adjusting the topological charge m and n. And in order to show the possible applications of these alterable foci pattern, some optical gradient force distributions were also calculated and illuminated. (C) 2014 Elsevier GmbH. All rights reserved.