Propagation characteristics of ultra-short Gaussian vortex beams

The propagation characteristics of pulsed Gaussian vortex beams are studied in this paper. The propagation equation and intensity distribution of the light beam are derived. The change law of some key parameters, such as the encircled energy radius and the red shift of the Gaussian vortex pulses are quantitatively calculated. It is found that encircled energy radius first increases and then decreases with the increase of the pulse width. When the pulse width is smaller, the space time coupling will affect the energy distribution of the light field. Spectral red shift presents rough exponential decay relationships to the pulse width. When the topological charge is relatively small, the spectral red shift increases quasi-linearly with the topological charge. Then with the increase of the topological charge, the spectral red shift tends to be slow, and finally tends to the asymptotic value.