Laguerre-Gaussian Mode Purity of Gaussian Vortex Beams

Abstract This paper focuses on the mode purity and beam propagation properties of Gaussian vortex beams which are Gaussian beams modulated by the spiral phase plates (SPP). For a given topological charge, the Laguerre-Gaussian beam has constant mode purity during its free space propagation. However, with the increase of the topological charge, the value of the highest mode purity decays. Our results imply that the modulation of SPP to the Gaussian beam is suitable for producing Laguerre-Gaussian beams with low topological charge, rather than with high topological charge.