Increasing the orbital angular momentum of a fractal beam

Optical vortices carrying the orbital angular momentum of light can be used as the advanced information carrier to encode quantum information in optical communications. As an effective method to give a large value of o ptical vortex charge to the light, we pro pose the method using a coherent superposition of many Gaussian beams with radial symmetry and self-similarity. By adjusting the initial phases of the constituent beams in a multibeam, the vortex charge at the beam center either becomes very large or evenly disappears. We find the optimal condition for the largest vortex charge.