The beam propagation factor and the kurtosis parameter of a Gaussian vortex beam

Abstract

Based on the definition of the second-order moment of intensity, the analytical expression for the beam propagation factor, namely the M2 factor, of a Gaussian vortex beam is derived, which is uniquely determined by the topological charge n. The numerical result indicates that the M2 factor of a Gaussian vortex beam increases with the increase of topological charge n. By means of the higher-order moment of intensity, the analytical expression for the kurtosis parameter of a Gaussian vortex beam passing through a paraxial ABCD optical system is also presented, which depends on topological charge n, parameter δ, transfer matrix elements A and D. When propagating in free space, the kurtosis parameter of a Gaussian vortex beam is determined by topological charge n and parameter δ. With the increase of parameter δ, the kurtosis parameter of a Gaussian vortex beam in free space first decreases and finally tends to a minimal value. Moreover, the kurtosis parameter of a Gaussian vortex beam in free space decreases with the increase of topological charge n. This research is helpful for the practical application of the Gaussian vortex beam.