Spacing dependent interaction of vortex dipole and induced off-axis propagations of optical energy

Abstract

Discussed analytically is the dynamics of a vortex dipole embedded in an elliptic Gaussian beam. Two opposite charged vortices of the vortex dipole can repel or attract each other, depending on whether their initial spacing larger or smaller than the critical value. While, stable vortex dipole with invariant spacing is predicated to exist at critical initial spacing. The critical spacing is dramatically related with the host elliptic beam. Furthermore, the dynamics of the vortex dipole can result in an off-axis propagation of optical beams, with propagating directions normal to the orientations of the vortex dipole. The optical beam exhibits larger off-axis velocity when the vortex dipole is parallel to the major axis of the host elliptic beam. The off-axis velocity can be further enhanced by increasing the ellipticity of host beams. The theoretical results can provide a controllable approach to change the propagating directions of optical beams by adjusting the initial spacing of vortex dipoles.