| Summary: | When the peak power exceeds many times the critical power of self-focusing, femtosecond vortex beams will break up into multiple filaments with random distribution because of the initial random noise, which is adverse to the applications. By numerical simulation we demonstrate that the use of the lens array can resist the influence of initial noise, leading to a regular distribution of multiple filaments. During the propagation, the filaments are symmetrically distributed on a ring and rotate around the beam center, thus forming helical filaments array. Besides, the rotation rate of the filaments can be controlled by changing the vortex radius, topological charge, and focusing condition.
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