Measuring the Topological Charge of Vortex Beams by the Cross Double-Slit Interference

In this paper, we propose a simple and feasible method to measure the topological charge of vortex beams using the cross double-slit interference pattern. The cross double-slit interference pattern can be considered as the superposition of the two single-slit diffraction patterns. It is found that the topological charge of the vortex beam is equal to the number of interference intensity period when the angle between the cross double-slit varies between 0 and 2π, the sign of the topological charge can be determined by the advance or delay of the intensity evolution when the phase π/2 is added on one slit of the cross double-slit.